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Matter In Our Surroundings

Question
CBSEENSC9006347

A car is moving with a uniform velocity of 54 kilometres per hour (km/h). What is the kinetic energy of a boy of mass 40 kg sitting in the car?

Solution

Velocity space of space the space boy comma space straight v space equals space Velocity space of space car space

Therefore comma

straight v space equals space fraction numerator 54 space km over denominator hour end fraction space equals space fraction numerator 54 space cross times space 1000 space straight m over denominator 3600 space straight s end fraction space equals space 15 space straight m divided by straight s

Mass space of space the space boy comma space straight m space equals space 40 space kg

straight K. straight E. space of space the space boy space equals space 1 half mv squared space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 1 half cross times 40 cross times left parenthesis 15 right parenthesis squared space
space space space space space space space space space space space space space space space space space space space space space space space space space space space space equals space 4500 space straight J.