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Matter In Our Surroundings

Question
CBSEENSC9006367

A body of mass 2 kg is thrown vertically upwards with an initial velocity of 20 m/s. What will be its potential energy at the end of 2 s ? (g = 10 m/s2)

Solution

G i v e n space t h a t comma space

M a s s space o f space t h e space b o d y comma space straight m space equals space 2 space k g

I n i t i a l space v e l o c i t y comma space space straight u space equals space 20 space straight m divided by straight s

Time space taken comma space straight t space equals space 2 space straight s

Acceleration space due space to space gravity comma space straight g space equals space minus 10 space straight m divided by straight s squared

H e i g h t space c o v e r e d space b y space t h e space b o d y space i n space 2 space i s space g i v e n space
b y space s e c o n d space e q u a t i o n space o f space m o t i o n comma space

T h a t space i s comma space
space space space space space space space space space straight s space equals space u t plus 1 half g t squared space
space space space space space space space space space space space space equals space 20 space cross times 2 space minus space 1 half cross times 10 cross times left parenthesis 2 right parenthesis squared space
space space space space space space space space space space space space equals space 40 minus 20 space equals space 20 space straight m

therefore space space space straight P. straight E. space o f space t h e space b o d y space a f t e r space 2 space straight s space equals space m g h

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 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 2 space cross times 10 cross times 20 space equals space 400 space straight J