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DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics PDF Download

Introductory Exercise 7.1

Q.1. Is the acceleration of a particle in uniform circular motion constant or variable?
Ans. 
Variable

In uniform circular motion the magnitude of acceleration DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics does not changewhile its direction (being always towards the centre of the circular path) changes.

Q.2. Is it necessary to express all angles in radian while using the equation ω = ω0 + αt?
Ans.
No

If ω0 and ω are in rad s-1 the value of a must be in rad s-2. But, if ω0 and ω are in degree s-1 the value of a must also be in degree s-2. Thus, it is not necessary to express all angles in radian. One way change rad into degree using π rad = 180°.

Q.3. Which of the following quantities may remain constant during the motion of an object along a curved path?
(i) Velocity
(ii) Speed
(iii) Acceleration
(iv ) Magnitude of acceleration
Ans.
speed, acceleration, the magnitude of acceleration.

During motion of an object along a curved path the speed and magnitude of its radial acceleration may remain constant. Due to change in direction of motion the velocity of the object will change even if its speed is constant. Further, the acceleration will also change even if the speed is constant.

Q.4. A particle moves in a circle of radius 1.0 cm with a speed given by v = 2 t where v is in cm/s and t in seconds.
(a ) Find the radial acceleration of the particle at t = 1 s.
(b) Find the tangential acceleration at t = 1 s.
(c) Find the magnitude of net acceleration at t = 1 s.
Ans. 
(a) 4.0 cms-2  (b) 2.0 cms-2 (c) 2√5 cms-2

(i) Radial acceleration (αc)
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
(ii) Tangential acceleration (αT )
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
(iii) Magnitude of net acceleration
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics 

Q.5. A particle is moving with a constant speed in a circular path. Find the ratio of average velocity to its instantaneous velocity when the particle describes an angle DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
Ans. 
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

Q.6. A particle is moving with a constant angular acceleration of 4 rad/sin a circular path. At time t =0, particle was at rest. Find the time at which the magnitudes of centripetal acceleration and tangential acceleration are equal.
Ans: 1/2 s

ωt = 0 + 4t
Centripetal acceleration = tangential acceleration
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

Introductory Exercise 7.2

Q.1. Is a body in uniform circular motion in equilibrium?

Ans. In uniform circular motion of a body the body is never in equilibrium as only one force (centripetal) acts on the body which forces the perform circular motion.

Q.2. Find the maximum speed at which a truck can safely travel without toppling over, on a curve of radius 250 m. The height of the centre of gravity of the truck above the ground is 1.5 m and the distance between the wheels is 1.5 m, the truck being horizontal.

Ans. DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
= 35 ms-1
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

Q.3. (a) How many revolutions per minute must the apparatus shown in figure make about a vertical axis so that the cord makes an angle of 45° with the vertical?
(b) What is the tension in the cord then. Given, l = √2 m, a = 20 cm and m = 5.0 kg?

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
Ans.

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

Q.4. A car moves at a constant speed on a straight but hilly road. One section has a crest and dip of the same 250 m radius.
(a) As the car passes over the crest the normal force on the car is one half the 16 kN weight of the car. What will be the normal force on the car as its passes through the bottom of the dip?
(b) What is the greatest speed at which the car can move without leaving the road at the top of the hill?
(c) Moving at a speed found in part (b) what will be the normal force on the car as it moves through the bottom of the dip? (Take g = 10 m/s2)
Ans.

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
(a) At rest :Required CPF = DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics...(i)
At dip :
Required CPF = N' - w
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics...(ii)
Comparing Eqs. (i) and (ii),
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
= 24 kN
(b) At crest on increasing the speed (v), the value of N will decrease and for maximum value of v the of N will be just zero.
Thus, DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
(c) At dip :
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
= w + mg
= 2w = 32 kN

Q.5. A car driver going at speed v suddenly finds a wide wall at a distance r. Should he apply brakes or turn the car in a circle of radius r to avoid hitting the wall.
Ans. 
Case I. If the driver turns the vehicle

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
[where v1 = maximum speed of vehicle]
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
Case II. If the driver tries to stop the vehicle by applying breaks.
Maximum retardation = μg
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
As v2 > v1, driver should apply breaks to stop the vehicle rather than taking turn.

Q.6. Show that the angle made by the string with the vertical in a conical pendulum is given by cos θ = DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics where L is the length of the string and ω is the angular speed.
Ans. 
In the answer to question 3(a) if we replace θ  by Φ

DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics
If θ is the angle made by the string with the vertical
DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics

The document DC Pandey Solutions: Circular Motion- 1 | DC Pandey Solutions for NEET Physics is a part of the NEET Course DC Pandey Solutions for NEET Physics.
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FAQs on DC Pandey Solutions: Circular Motion- 1 - DC Pandey Solutions for NEET Physics

1. What is circular motion?
Ans. Circular motion refers to the movement of an object along a circular path, where the object continuously changes its direction. It involves the concepts of centripetal force, tangential velocity, and radial acceleration.
2. How is circular motion related to NEET exam?
Ans. Circular motion is an important topic in the NEET exam as it is a fundamental concept in physics. Questions related to circular motion can be asked in the physics section of the NEET exam, where students are tested on their understanding of centripetal force, angular velocity, and other related concepts.
3. What is centripetal force and how is it related to circular motion?
Ans. Centripetal force is the force that acts towards the center of a circular path and keeps an object moving in a circular motion. In circular motion, the centripetal force is responsible for changing the direction of the object's velocity, even though the magnitude of the velocity remains constant.
4. How can I calculate the centripetal force in circular motion?
Ans. The centripetal force can be calculated using the equation Fc = (mv^2)/r, where Fc is the centripetal force, m is the mass of the object, v is the velocity of the object, and r is the radius of the circular path.
5. Are there any real-life examples of circular motion?
Ans. Yes, there are several real-life examples of circular motion. Some examples include the motion of planets around the sun, the rotation of a carousel, the swinging of a pendulum, and the motion of a car around a curved road.
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