HARD
9th CBSE
IMPORTANT
Earn 100

In which of the following cases will the work done by a force be maximum: When the angle between the direction of force and displacement is, (i) zero (ii) 90°?

Important Questions on Work and Energy

HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 5
Is it possible that a force acts on a body, and still work done is zero? Support your answer by two examples.
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 6
State in each of the following cases, if work is done or not done, and why?
(a) A man pushing a wall.
(b) A girl climbing a staircase.
(c) A swimmer swimming in water.
(d) A standing man holding a suitcase in his hand.
(e) A lady cooking food.
(f) A porter carrying a heavy load, going down the stairs.
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 1
The velocity of a body moving in a straight line is increased by applying a constant force F, for some distance in the direction of the motion. Prove that the increase in the kinetic energy of the body is equal to the work done by the force on the body.
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 2
It is possible that an object is in the state of accelerated motion due to external force due to on it, but no work is being done by the force. Explain it with an example.
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 3
A boy is moving on a straight road against a frictional force of 5 N. After travelling a distance of 1.5 k m he forgot the correct path at a round about of radius 100 m. However, he moves on the circular path for one and half cycle, and then he moves forward up to 2.0 km. Calculate the work done by him.
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 1
A girl having mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of 4 ms-1 by applying a force. The trolley comes to rest after traversing distance of 16 m. (a) How much work is done on the trolley ? (b) How much work is done by the girl ?
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>EXERCISE>Q 2
Four men lift 250 kg box to a height of 1 m and hold it without raising or lowering it. (a) How much work is done by the men in lifting the box? (b) How much work do they do in just holding it? (c) Why do they get tired while holding it ? (g=10 m s-2)
HARD
9th CBSE
IMPORTANT
Core Science Physics For Class 9>Chapter 4 - Work and Energy>Practice Problems>Q 1
A water tank top of a building 25 m high contains 100 k g  of water. Calculate the potential energy stored in the water (Take the gravitational acceleration g=10 m s-2).