SLS College of Sciences & Arts
Physics Chapter 4(Work & Energy)
Q.1) A bucket is taken to the bottom of a well, does the bucket possess any P.E
Explain?
Answer:
Yes, a bucket does possess the potential energy.
When we lower the bucket to the bottom of the well, water exerts a thrust on the bucket in the
upward direction. So, we have to do some work against that upthrust of water to take the bucket
to bottom of well. This work done is stored in form of potential energy in the bucket. So, we can
say that bucket possess negative of potential energy if we take the ground level as a reference
level.
Q.2) When an arrow is shot from its bow, it has k.E. From where does it get
the k.E?
Answer:
When we stretch the string of the bow to shot the arrow, some work is done on the bow. This
work done is stored in the bow in form of elastic potential energy.
When we release the string of the bow and shot the arrow, the stored P.E of the bow will convert
in form of K.E of arrow making it capable of moving in the forward direction.
So, we can say that the arrow gets its K.E from the P.E of the bow.
Q.3) Does a hydrogen filled balloon possess any P.E? Explain?
Answer:
Yes, a hydrogen filled balloon does possess P.E.
Hydrogen is a lighter gas than air, so when we fill a balloon with hydrogen gas and release it in
air, it starts moving upward against the gravitational field.
So, due to upthrust of air on the balloon, some work is done on the balloon which will store in
form of P.E in balloon.
Q.4) Is K.E a vector quantity?
Answer:
No, K.E is not a vector quantity. It is a scalar quantity.
As K.E is given by,
Where “m” represents the mass of an object which is a scalar quantity and “v2” represents the
magnitude of the velocity of the object which is also a scalar quantity. That’s why K.E is also a
scalar quantity.
Q.5) What happens to K.E of a bullet when it penetrates into a target?
Answer:
K.E of the bullet become smaller and smaller as it penetrates to the target.
When a bullet penetrates to a target, target exerts a resisting force on the bullet. Some of K.E of
the bullet is used to overcome that resisting force offered by the target. While some part of K.E
converts into other forms of energy such as sound energy.
Q.6) Does the tension in the string of a swinging pendulum do any work?
Explain.
Answer:
Work done is defined as the product of the force applied to a body and the displacement covered
