Q21 of 28 Page 159

When the speed of a ball is doubled its kinetic energy

(a) Remains same


(b) gets doubled


(c) Becomes half


(d) becomes 4 times

B

Explanation: Because kinetic energy is directly proportional to square of speed


Kinetic Energy = --- (i)


If speed becomes doubled then V= 2v putting in the equation we have now new Kinetic Energy = --(ii)


Dividing Eq (ii) and (i) , We will get New Kinetic Energy as 4 times than the older one.


More from this chapter

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19

Find the mass of a body which has 5J of kinetic energy while moving at a speed of 2m/s.

 20

A cycle together with its rider weighs 100kg. How much work is needed to set it moving at 3 m/s.

 22

Two bodies of unequal masses are dropped from the top of building. Which of the following is equal for both bodies at any instance?

(a) Speed


(b) force of gravity


(c) potential energy


(d) kinetic energy

 23

A man with a box on his head is climbing up a ladder. The work done by the man on the box is

(a) Positive


(b) Negative


(c) Zero


(d) Undefined.