Question

A body of mass 2 kg is thrown up vertically with a kinetic energy of 490 J.If the acceleration due to gravity is 9.8 m/s^2, the height at which the kinetic energy of the body becomes half of the original value is -

a) 50 m

b) 25 m

c) 12.5 m

d) 10 m

Answer 1

@Hero @hartnn @Chlorophyll @robtobey @sauravshakya @kropot72 @jiteshmeghwal9 @hba

Answer 2

@mathslover have a look:)

Answer 3

First find the original value ... what you get?

Answer 4

original value????

Answer 5

sorry i think it is given

Answer 6

Potential energy of the body =mgh

Answer 7

u know it?

Answer 8

ok!!

Answer 9

yaa

Answer 10

490 J = KE (ORIGINAL)

Answer 11

yaa

Answer 12

half of it will be 490 /2 J = 245 J , correct?

Answer 13

why you do the half the K.E @mathslover

Answer 14

@mayankdevnani because we have to find the height when the new kinetic energy equals half of the original one. ...

Answer 15

@03225186213

Answer 16

therefore the new kinetic energy must be equal to 245 Joules.

Answer 17

yaa

Answer 18

correct!!!

Answer 19

therefore we have : 1/2 m v^2 = 245 J

1/2 m (u^2 + 2gh ) = 245 J

1/2 m (2gh) = 245

mgh = 245 J

2 kg * 9.8 * h = 245

Answer 20

solve for h and you will get h = 12.5 m

Answer 21

1/2 m (u^2 + 2gh ) = 245 J ??????????????

Answer 22

got it?

Answer 23

no!!!!

Answer 24

1/2 m (u^2 + 2gh ) = 245 J
this line!!!

Answer 25

since v^2 = u^2 + 2gh

therefore..

Answer 26

ok

Answer 27

thnx.... i got it @mathslover

Answer 28

good,...

Answer 29

let @03225186213 be answer.... plz wait

Answer 30

1/2 mv^2=mgh
490/2=2 (-9.8)h h= -9.8
because it is moving against gravity

Answer 31

@03225186213 same I thought BUT it is given in the quest. that g = 9.8 m/s^2

Answer 32

yaaa you are correct thnx @mathslover and @03225186213

Answer 33

welcome

Answer 34

:)