An object of 40 kg in raised to a height of 5m above the ground. What is its potential energy? If the object is allowed to fall, find its Kinetic energy when it is half-way down. (g = 10 ms–2)

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Chapter 10

NCERT

Class 9

Science

Solutions

10. An object of 40 kg in raised to a height of 5m above the ground. What is its potential energy? If the object is allowed to fall, find its Kinetic energy when it is half-way down. (g = 10 ms–2)

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Question:

An object of 40 kg in raised to a height of 5m above the ground. What is its potential energy? If the object is allowed to fall, find its Kinetic energy when it is half-way down. (g = 10 ms^–2)

Answer:

(i) Mass of the object m = 40 kg

Height h = 5m

Acceleration due to gravity,

g = 10 ms^–2

∴ Potential energy = mgh

= 40 kg × 5m × 9.8 ms^–2

= 1960J

(ii) Halfway down, the potential energy will be = 1960 J/2.

= 980J

(iiI) Energy changes from one form of energy into another form of energy. The potential energy will be equal to kinetic energy; the half-way down the kinetic energy will be 980J.

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