CBSE 11th PHYSICS- Solved Examples

Question 1 Force exerted on a body changes it's

(a) Direction of motion

(b) Momentum

(c) Kinetic energy

(d) All the above

Solution: A body acted upon by a certain force produces acceleration i.e. it undergoes change in it's velocity. hence choice (d) is correct

Question 2 there are two statements

A Rate of change of momentum corresponds to force

B Rate of change of momentum corresponds to Kinetic Energy

Which of the following is correct

(a) A only

(b) B only

(c) Both A and B are correct

(d) Both A and B are wrong

Solution 

F=dp/dt so a is correct

Question 3 A truck and car are moving on a plane road with same kinetic Energy. They are brought to rest by application of brakes which provide equal retarding forces. Which of the following statements is true.

(a) Distance traveled by truck is shorter then car before coming to rest 

(b) Distance traveled by car is shorter then truck before coming to rest

(c) Distance traveled depends on individual velocity of both the vehicles

(d) Both will travel same distance before coming to rest

Solution 3

By work energy theorem we know

KE_f-KE_i=Workdone

So in this case

Initial KE=retarting force * distance traveled

Since kinetic energy is same and retarding force is equal

Distance traveled will be same

Question 4 A block A of mass m₁ is released from top of smooth inclined plane and it slides down the plane. Another block of mass m₂ such that m₂ > m₁is dropped from the same point and falls vertically downwards. Which one of the following statements will be true if the friction offered by air is negligible?

(a) Both blocks will reach ground at same time

(b) Both blocks will reach ground with the same speed

(c) speed of both the blocks when they reach ground will depend on their masses

(d) Block A reaches ground before block B

Solution 4

since velocity of block when it reaches the ground is given by v=(2gh)^1/2 and it is independent of the mass the correct choice will be (b). 

Question 5 Which of the following observer is/are non inertial

a.A child revolving in the merry ground

b. A driver in a train moving with constant velocity v

c. A passenger in a bus which is slowing down to a stop

d None of these 

Solution 5

Since centripetal acceleration is present in merry round it is non inertial frame of reference

Since bus is slowing down to a stop,it means it is experiencing a retardation ,so it is non inertial frame of reference