Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

NEET: Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

The document Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET is a part of the NEET Course Physics Class 11.
All you need of NEET at this link: NEET

Q.1. A particle is released from height S from the surface of the earth. At a certain height, its kinetic energy is three times its potential energy. The height from the surface of the earth and the speed of the particle at that instant are respectively:          [2021]
(a) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

(b) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(c) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(d) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Ans: B
U + KE = E
4U = E = mgS
4mgh = mgS
h = S/4
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.2. Water falls from a height of 60 m at the rate of 15 kg/s to operate a turbine. The losses due to frictional force are 10% of the input energy. How much power is generated by the turbine?(g = 10 m/s2)        [2021]
(a) 12.3 kW
(b) 7.0 kW
(c) 10.2 kW
(d) 8.1 kW
Ans:
 
D
Mass of water falling/second = 15 kg/s h = 60 m, g = 10 m/s2, loss = 10 % i.e., 90% is used. Power generated = 15 x 10 x 60 x 0.9 = 8100 W = 8.1 kW.

Q.3. The energy required to break one bond in DNA is 10–20J. This value in eV is nearly:        [2020]
(a) 0.06 
(b) 0.006 
(c) 6 
(d) 0.6
Ans: a

1.6 × 10–19 Joule = 1 eV
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.4. Body A of mass 4m moving with speed u collides with another body B of mass 2m, at rest. The collision is head on and elastic in nature. After the collision the fraction of energy lost by the colliding body A is:    [2019]
(a) 1/9
(b) 8/9
(c) 4/9
(d) 5/9
Ans:
b

Fractional loss of KE of colliding body
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.5. A disc of radius 2 m and mass 100 kg rolls on a horizontal floor. Its centre of mass has speed of 20 cm/s. How much work is needed to stop it?    [2019]
(a) 3 J
(b) 30 kJ
(c) 2 J
(d) 1 J
Ans:
a

Work required = change in kinetic energy Final KE = 0
Initial KE Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
|ΔKE| = 3 J

Q.6. A force F = 20 + 10 y acts on a particle in y direction where F is in newton and y in meter. Work done by this force to move the particle from y = 0 to y = 1 m is    [2019]
(a) 30 J
(b) 5 J
(c) 25 J
(d) 20 J
Ans
: c

Work done by variable force is
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.7. The work done to raise a mass m from the surface of the earth to a height h, which is equal to the radius of the earth, is:    [2019]
(a) mgR
(b) 2mgR
(c)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(d)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Ans:
c

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Initial potential energy at earths surface is
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Final potential energy at height h = R
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
As work done = Change in PE∴ W = Uf – Ui
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET (∵ GM = gR2)

Q.8. A moving block having mass m, collides with another stationary block having mass 4m. The lighter block comes to rest after collision. When the initial velocity of the lighter block is v, then the value of coefficient of restitution (e) will be :-    [2018]
(a) 0.5
(b) 0.25
(c) 0.8
(d) 0.4
Ans
: b

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.9. A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter AB = D. The height h is equal to    [2018]
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(a) 3/2 D
(b) D
(c) 7/5 D
(d) 5/4 D
Ans:
d

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.10. The kinetic energies of a planet in an elliptical orbit about the Sun, at positions A, B and C are KA, KB and KC respectively. AC is the major axis and SB is perpendicular to AC at the position of the Sun S as shown in the figure. Then    [2018]
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(a) KA < KB < KC
(b) KA > KB > KC
(c) KB < KA < KC
(d) KB > KA > KC
Ans:
b

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.11. A spring of force constant k is cut into lengths of ratio 1: 2 : 3. They are connected in series and the new force constant is k'. Then they are connected in parallel and force constant is k''. Then k' : k'' is    [2017]
(a) 1 : 6
(b) 1 : 9
(c) 1 : 11
(d) 1 : 14
Ans:
c

Force constant of spring
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
after cutting the spring in the ratio 1:2:3, the force constants will be in the ratio 6:3:2
Force constant in series K' is given by Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Force constant in parallel K" : 6k+3k+2k = 11k;
hence K'/K" = 1/11

Q.12. Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take 'g' constant with a value 10 m/s2. The work done by the    [2017]
(i) gravitational force and the
(ii) resistive force of air is :-
(a) (i) 1.25 J (ii) – 8.25 J
(b) (i) 100 J (ii) 8.75 J
(c) (i) 10 J (ii) – 8.75 J
(d) (i) – 10 J (ii) – 8.25 J
Ans:
c

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.13. A body of mass 1 kg begins to move under the action of a time dependent force Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET , whenPrevious year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEETare unit vectors along x and y axis. What power will be developed by the force at the time t ?    [2016]
(a) (2t3+ 3t5)W
(b) (2t2 + 3t3)W
(c) (2t2 + 4t4)W
(d) (2t3 + 3t4)W
Ans:
a

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.14. Two particles of masses m1, m2 move with initial velocities u1 and u2. On collision, one of the particles get excited to higher level, after absorbing energy ε. If final velocities of particles be v1 and v2 then we must have :    [2015]
(a) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(b)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(c) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(d) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Ans:
d

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.15. Two similar springs P and Q have spring constants KP and KQ, such that KP > KQ. They are stretched, first by the same amount (case a), then by the same force (case b). The work done by the springs WP and WQ are related as, in case (a) and case (b), respectively:    [2015]
A: WP < WQ; WQ < WP
B: WP = WQ; WP > WQ
C: WP = WQ; WP = WQ
D: WP > WQ; WQ > WP

Ans: d

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.16. A mass m moves in a circle on a smooth horizontal plane with velocity v0 at a radius R0. The mass is attached to a string which passes through a smooth hole in the plane as shown.

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

The tension in the string is increased gradually and finally m moves in a circle of radius R0/2. The final value of the kinetic energy is :    [2015]
(a)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(b) Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(c)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
(d)Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Ans: 
d


When a mass moves in a circle of radius R0 with velocity v0, its kinetic energy is given by

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
The tension in the string is gradually increased and the radius of the circle decreased to R0/2. When the radius of the circle is R  Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET the tension in the string is the same as the centripetal force.

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
where L = mRv is the angular momentum which is conserved.
Work done in reducing the radius of the circle from R0 to R0/2 is

Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET

Q.17. A block of mass 10 kg, moving in x direction with a constant speed of 10 ms-1, is subjected to a retarding force F = 0.1 x J/m during its travel from x = 20 m to 30 m. Its final KE will be :    [2015]
(a) 250 J
(b) 475 J
(c) 450 J
(d) 275 J
Ans: b
The block of mass M = 10 kg is moving in the x - direction with a speed v = 10 m/s. Its initial kinetic energy is
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
It is subjected to a retarding force F = 0.1 x J/m during its travel from x = 20 m to 30 m.
Work done is given by
Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET
Final kinetic energy is, KEf = KEi + W = 500 - 25 = 475
The document Previous year questions (2014-21): Work, Energy & Power Notes | Study Physics Class 11 - NEET is a part of the NEET Course Physics Class 11.
All you need of NEET at this link: NEET
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