Q1.
Calculate the kinetic energy of a body of mass 5 kg moving with a velocity of 0.5 m/s.
Q2.
Find the velocity of a body of mass 100 g having a kinetic energy of 20 J.
Q3.
A light and a heavy body have equal kinetic energy. Which one is moving fast?
Explain your answer.
Q4.
A body of mass 10 kg initially at rest is subjected to a force of 40 N. What is the kinetic energy acquired by the body at the end of 5 s?
Q5.
A mass of 10 kg is dropped from a height of 10 m. Find its :
(i) Kinetic energy (ii) Velocity
just as it reaches the ground. (Take g = 9.8 m/s2)
Q6.
The momentum of a bullet of mass 20 g fired from a gun is 10 kg m/s. Determine the kinetic energy of the bullet after firing.
Q7.
A coolie is walking on a railway platform with a load of 27 kg on his head. What is the amount of work done by him?
Q8.
A ball lying at rest is pushed in such a manner that it attains a velocity of 12m/s over a distance of 1.2 m. Calculate the work done if the mass of the ball is 50g.
Q9.
What is the work done by the force of gravity in the following cases?
(a) Satellite moving around the earth in a circular orbit of radius 35000 km.
(b) A stone of mass 250 g is thrown up through a height of 2.5 m. (take g = 10 9.8 m/s2)
Q10.
There are three pictures given below. They represent the direction of applied force and displacement produced in three different bricks. If a force of 5 N is applied in each case and displacement produced is also 10m in each case, then find out the work done by the force in each case.
Q11.
The kinetic energy of an object of mass ‘M’ moving with a velocity of 5 m/s is 75 J. What will be its kinetic energy when its velocity is doubled?
Q12.
If the velocity of a body is doubled its kinetic energy
(a) gets doubled
(b) becomes half
(c) does not change
(d) becomes 4 times
Q13.
An iron sphere of mass 10 kg has the same diameter as an aluminium sphere of mass is 3.5 kg. Both spheres are dropped simultaneously from a tower. When they are 10 m above the ground, they have the same
(a) acceleration
(b) momenta
(c) Gravitational force
(d) kinetic energy
Q14.
Assertion : No work is done against gravity when a woman carrying a load on her head, walks on a level road with a uniform velocity.
Reason : No work is done if the applied force is not able to displace the object.
Q15.
Assertion : A light body and heavy body have same momentum. Then they also have same kinetic energy.
Reason : Kinetic energy depends on mass of the body.
Answer key for numericals
Ans 1: 0.625 J
Ans 2: 20 m/s
Ans 4: 2000 J
Ans 5: KE = 980 J v = 14 m/s
Ans 6: 2500 J
Ans 8: 3.6 J
Ans 9: (b) – 6.25 J
Ans11: 300 J
