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JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR PDF Download

Q 1.  A particle (m = 1 kg) slides down a frictionless track (AOC) starting from rest at a point A (height 2 m). After reaching C, the particle continues to move freely in air as a projectile. When it reaches its highest point P (height 1 m), the kinetic energy of the particle (in J) is (Figure drawn is schematic and not to scale; take g = 10 m/s2) ______.    [2020]
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans: 
10
Solution:
Given that m = 1 kg, g = 10 m/s2 , h1 = 2 m and h2 = 1 m.
According to law of conservation of energy, we have
Energy at point A = Energy at point P
⇒ (Potential energy + Kinetic energy)A = (Potential energy + Kinetic energy)P
⇒ mgh1 + K1 + mgh2 + K2
Since, K1 = 0. So,
2mg + 0 = mg + K2
⇒ K2 = mg
= 1 x 10 = 10 J

Q 2. An elevator in a building can carry a maximum of 10 persons, with the average mass of each person being 68 kg. The mass of the elevator itself is 920 kg and it moves with a constant speed of 3 m/s. The frictional force opposing the motion is 6000 N. If the elevator is moving up with its full capacity, the power delivered by the motor to the elevator (g = 10 m/s2 ) must be at least 
(1) 56300 W 
(2) 62360 W 
(3) 48000 W 
(4) 66000 W
Ans: (4)
Solution:
Given that

Capacity of elevator, C = 10 persons

Average mass of each person, mp = 68 kg

Mass of elevator, me = 920 kg

Speed of elevator, v = 3 m/s

Frictional force, f = 600 N
Force acting on motor is given by,
F = mtotal x g + f
= ( 10 x 68 + 920) x 10 + 6000
=16000 + 6000
= 22000
So, power delivered by motor is  P = F x v
= 22000 x 3 = 66000 W
Therefore, power delivered by the motor to the elevator must be at least 66000 W.

Q 3. A body A, of mass m = 0.1 kg has an initial velocity of JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR It collides elastically with another body, B of the same mass which has an initial velocity of  JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR After collision, A moves with a velocity JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR The energy of B after collision is written as (x/10) J. The value of x is ______. 
Ans: 1
Solution:
Given that
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Since, collision is elastic so by the conservation of linear momentum
Initial momentum = Final momentum
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Kinetic energy of B after collision is
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Therefore, x = 1

Q 4. A particle of mass m is dropped from a height h above the ground. At the same time, another particle of the same mass is thrown vertically upwards from the ground with a speed of  JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR If they collide head-on completely inelastically, the time for the combined mass to reach the ground, in units of JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR is    [2020]
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans:  (4)
Solution:
Given that
mA = mB = m, v0,A = v0,B =  JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR 
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Time for collision is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
velocity before collision is
vi,A = gt, vi,B = V0,B - gt
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
⇒ vi,A = -vi,B
From conservation of momentum, we have
mAvi.A + mBvi,B = mAvf,A + mBvf,B
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
So, height from ground is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 5. Consider a force  JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR The work done (in J) by this force in moving a particle from point A(1, 0) to B(0, 1) along the line segment given in the fiigure is (all quantities are in SI units)     [2020]
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(1) 2 
(2) 1/2
(3) 1
(4) 3/2
Ans: (3)
Solution:
Given that
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Work done by the force is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 6. Two particles of equal mass m have respective initial velocities JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR They collide completely inelastically. The energy lost in the process is     [2020]
(1) 1/3 mμ2
(2) 1/8 mμ2
(3) 3/4 mμ2
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans: (2)
Solution:
Given that
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Since collision is inelastic only momentum is conserved. So,
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Change in kinetic energy is given by
ΔK = Kf - Ki
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 7. A particle of mass m is projected with a speed u from the ground at an angle θ =π/3 w.r.t. horizontal (x-axis). When it has reached its maximum height, it collides completely inealstically with another particle of the same mass and velocity JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR. The horizontal distance covered by the combined mass before reaching the ground is    [2020]
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans: (1)
Solution:
Given that initial speed u, angle of projection from ground θ = π/3
Speed of particle at height point is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Applying conservation of momentum, we have
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Time of flight after collision is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Range after collision is given by
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 8. A block of mass m, lying on a smooth horizontal surface, is attached to a spring (of negligible mass) of spring constant k. The other end of the spring is fixed, as shown in the figure. The block is initially at rest in its equilibrium position. If now the block is pulled with a constant force F, the maximum speed of the block is    (2019)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(1) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(2) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(3) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(4) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans:
(4)
Solution: 
The maximum speed of block is at mean position F = kx    (equilibrium)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
According to work energy theorem,
Work done by external force + work done by spring = Change in kinetic energy
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 9. Three blocks A, B and C are lying on a smooth horizontal surface, as shown in the figure. A and B have equal masses 'm', while C has mass 'M'. Block A is given an initial speed v toward B due to which it collides with B perfectly inelastically. The combined mass collides with C, also perfectly inelastically and 5/6th of the initial kinetic energy is lost in whole process. What is value of M/m?    (2019)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

(1) 5
(2) 2
(3) 4
(4) 3
Ans:
(3)
Solution:
From the linear momentum, we have
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Now, according to the question,
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 10. A force acts on a 2 kg object so that its position is given as a function of time as x = 3t2 + 5. What is the work done by this force in first 5 s?    (2019)
(1) 850 J
(2) 950 J
(3) 875 J
(4) 900 J
Ans: 
(4)
Solution:
The position of object as a function of time is given by
x = 3t2 + 5             -----(1)
We know that
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Differentiating w.r.t. Eq. (1) becomes
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Therefore, work done by the force = change in K.E.
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 11. A block of mass m is kept on a platform which starts from rest with constant acceleration g/2 upward, as shown in the figure. Work done by normal reaction on block in time t is    (2019)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(1) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(2) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(3) 0
(4) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans: 
(4)
Solution:
According to the Newton second law
F = ma
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Work done is
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 12. A piece of wood of mass 0.03 kg is dropped from the top of a 100 m height building. At the same time, a bullet of mass 0.02 kg is fired vertically upward, with a velocity 100 m/s, from the ground. The bullet gets embedded in the wood. Then the maximum height to which the combined system reaches above the top of the building before falling below is (g = 10 m/s2)    (2019)
(1) 20 m
(2) 30 m
(3) 40 m
(4) 10 m
Ans:
(3)
Solution:
Bullet will collide with piece of wood at
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Velocity of piece of wood u = 0 + 10 × 1 = 10 m/s
Velocity of bullet v = 100 – 10 = 90 m/s
From conservation of linear momentum,
−(0.02) (1v) + (0.02) (9v) = (0.05)
⇒ 150 = 5v
⇒ v = 30 m/s
Maximum height reached by body is
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
At time of collision system is h distance below top of tower
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Therefore, height above tower = 45 – 5 = 40 m

Q 13. A particle which is experiencing a force, given by JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR undergoes a displacement of JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR If the particle had a kinetic energy of 3 J at the beginning of the displacement, what is its kinetic energy at the end of the displacement?    (2019)
(1) 9 J
(2) 12 J
(3) 10 J
(4) 15 J
Ans: 
(4)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
According to work-energy theorem
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 14. A body of mass 1 kg falls freely from a height of 100 m on a platform of mass 3 kg which is mounted on a spring having spring constant k = 1.25 × 106 N/m. The body sticks to the platform and the spring’s maximum compression is found to be x. Given that g = 10 m/s2, the value of x will be close to     (2019)
(1) 8 cm
(2) 4 cm
(3) 80 cm
(4) 40 cm

Ans: None of the above (*)
* None of the options is correct
Solution:
Initial compression is mg = kx
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Velocity of 1 kg block just before it collides with 3 kg block
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Applying momentum conversation just before and just after collision, we have
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Now, applying work-energy theorem,
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 15. An alpha-particle of mass m suffers one-dimensional elastic collision with a nucleus at rest of unknown mass. It is scattered directly backward losing, 64% of its initial kinetic energy. The mass of the nucleus is    (2019)
(1) 2m
(2) 3.5m
(3) 1.5m
(4) 4m
Ans: 
(4)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Applying law of conservation of momentum before collision,
mu1 + 0 = −mv1 + Mv2
⇒ mu1 = −mv1 + Mv2     (1)
Since, α-particle is scattered in backward thus, losing 64% of initial energy.
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Now, coefficient of restitution
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
thus
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 16. A particle is moving in a circular path of radius 'a' under the action of an attractive potential JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR  Its total energy is:     (2018)
(1) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(2) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(3) Zero
(4) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans:
(3)
Solution:

JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
‘ – ‘ sign of force implies attractive force So,
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 17. In a collinear collision, a particle with an initial speed ν0 strikes a stationary particle of the same mass. If the final total kinetic energy is 50% greater than the original kinetic energy, the magnitude of the relative velocity between the two particles, after collision, is:    (2018)
(1) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(2) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(3) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(4) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans:
(2)
Solution:
By conservation of linear momentum,
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
So relative velocity :
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Hence the Solution is Option (2)

Q 18. A particle is moving with a uniform speed in a circular orbit of radius 'R' in a central force inversely proportional to the nth power of R. If the period of rotation of the particle is T, then:    (2018)
(1) Tα R3/2 for any n.
(2) JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(3) Tα R(n+1)/2
(4) Tα Rn/2
Ans: 
(3)
Solution:

JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 19. A body of mass m starts moving from rest along x-axis so that its velocity varies as v = a√s where a is a constant and s is the distance covered by the body. The total work done by all the forces acting on the body in the first 't' seconds after the start of the motion is:    (2018)
(1) (8) ma4t2
(2) (1/4) ma4t2
(3) (4) ma4t2
(4) (1/8) ma4t2
Ans: 
(4)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 20. Two particles of the same mass m are moving in circular orbits because of force given by JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR. The first particle is at distance r =  1 and the second at r = 4. The best estimate for the ratio of kinetic energies of the first and the second particle is closest to    (2018)
(1) 3 × 10–3

(2) 6 × 102
(3) 6 × 10–2
(4) 10–1
Ans:
(3)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 21.  A body of mass m = 10–2 kg is moving in a medium and experiences a frictional force F = –kv2. Its initial speed is v0 = 10 ms–1. If after 10 s, its energy is 1/8 mv02, the value of k will be    (2017)
(1) 10–4 kg m–1
(2) 10-1 kg m–1 s-1
(3) 10-3 kg m-1
(4) 10-3 kg s-1
Ans:
(1)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 22.  A time dependent force F = 6t acts on a particle of mass 1 kg. If the particle starts from rest, the work done by the force during the first 1 second will be    (2017)
(1) 9 J
(2) 18 J
(3) 4.5 J
(4) 22 J
Ans: 
(3)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 23. An object is dropped from a height h from the ground. Every time it hits the ground it loses 50% of its kinetic energy. The total distance covered in t → ∞ is -    (2017)
(1) 3h
(2) ∞
(3) 5/3h
(4) 8/3h
Ans: 
(1)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 24.  Two particles A and B of equal mass M are moving with the same speed u as shown in the figure. They collide completely inelastically and move as a single particle C. The angle q that the path of C makes with the X-axis is given by-    (2017)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
Ans:
(4)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 25.  A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times. Assume that the potential energy lost each time he lowers the mass is dissipated. How much fat will he use up considering the work done only when the weight is lifted up? Fat supplies 3.8 x 107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate. (Take g = 9.8 ms-2):    (2016)
A: 2.45 x 10-3 kg
B: 6.45 x 10-3 kg
C: 9.89 x 10-3 kg
D: 12.89 x 10-3 kg
Ans:
D
Solution:
0.2 x 3.8 x 107 x m = 10 x g x 1 x 1000
m = JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
 = 1.289 x 10-2 Kg
= 12.89 x 10-3 Kg

Q 26. Velocity- time graph for a body of mass 10 kg is shown in figure. Work- done on the body in first two seconds of the motion is:     (2016)
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
(1) 12000 J
(2) –12000 J
(3) –4500 J
(4) –9300 J
Ans: 
(3)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

Q 27. A particle of mass m is acted upon by a force F given by the empirical law JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR If this law is to be tested experimentally by observing the motion starting from rest, the best way is to plot:    (2016)
(1) log v(t) against t
(2) v(t) against t2
(3) log v(t) against 1/t2
(4) log v(t) against 1/t
Ans:
(4)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR
logV vs 1/t will be a st. line curve.

Q 28. A particle of mass M is moving in a circle of fixed radius R in such a way that its centripetal acceleration at time t is given by n2 R t2 where n is a constant. The power delivered to the particle by the force acting on it, is:    (2016)
(1) M n R2 t2
(2) 1/2 Mn2R2t2
(3) Mn2R2t
(4) MnR2t
Ans: 
(3)
Solution:
JEE Main Previous Year Questions (2016- 2024): Work, Energy and Power | Physics for Airmen Group X - Airforce X Y / Indian Navy SSR

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