Class – XI
Force and Laws Of Motion
1. Why do we fall forward when a moving bus suddenly stops Explain?
2. A bullet of mass 60g moving with a velocity of 500 ms-1 is brought to rest in 0.01 s.Find the
impulse and average force of blow.
3. A woman weighing 50 kgf stands on a weighing machine placed in a lift.What will be the
reading of the machine when the lift is
a. moving upwards with a uniform velocity of 5 ms-1.
b. moving downwards with a uniform acceleration of 1 ms-2?(Take g=10 ms-2)
4. A shell of mass 10 kg moving with a velocity of 20 ms-1 explodes in to two portions of 6kg and
4kg respectively .if the former is just brought to the rest after explosion ,find the velocity of
latter.
5. State Newton’s second law of motion .Show that it is real law of the motion.
6. State and prove impulse-momentum theorem.
7. Discuss the motion of two bodies of different masses connected at the ends of a light
inextensible string, which goes over a frictionless and massless pulley.
8. State and prove principle of conservation of linear momentum. Apply this law to explain why
a. Gun recoils, when fired.
b. A rocket goes up ,when fired
c. The boat moves away ,when a man jumps from it to the shore.
9. A lift is moving down with an acceleration of 3ms-2 .A bal is released 1.7 m above the lift floor.
Assuming (g=9.8 ms-2) how long ball take to hit the floor?
10. A wooden block weighing 200g is attached to hanger weighing 45g with a fine thread .The block
is placed on a frictionless surface and after passing thread over a smooth pulley ,hanger is
allowed to pull the block. Find the acceleration of the system and tension in the String.