mayankdevnani
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
Delete
Share
This Question is Closed
mayankdevnani
Best Response
You've already chosen the best response.
1
@Hero @hartnn @Chlorophyll @robtobey @sauravshakya @kropot72 @jiteshmeghwal9 @hba
mayankdevnani
Best Response
You've already chosen the best response.
1
@mathslover have a look:)
mathslover
Best Response
You've already chosen the best response.
2
First find the original value ... what you get?
mayankdevnani
Best Response
You've already chosen the best response.
1
original value????
mathslover
Best Response
You've already chosen the best response.
2
sorry i think it is given
sauravshakya
Best Response
You've already chosen the best response.
0
Potential energy of the body =mgh
sauravshakya
Best Response
You've already chosen the best response.
0
u know it?
mayankdevnani
Best Response
You've already chosen the best response.
1
ok!!
mayankdevnani
Best Response
You've already chosen the best response.
1
yaa
mathslover
Best Response
You've already chosen the best response.
2
490 J = KE (ORIGINAL)
mayankdevnani
Best Response
You've already chosen the best response.
1
yaa
mathslover
Best Response
You've already chosen the best response.
2
half of it will be 490 /2 J = 245 J , correct?
mayankdevnani
Best Response
You've already chosen the best response.
1
why you do the half the K.E @mathslover
mathslover
Best Response
You've already chosen the best response.
2
@mayankdevnani because we have to find the height when the new kinetic energy equals half of the original one. ...
mayankdevnani
Best Response
You've already chosen the best response.
1
@03225186213
mathslover
Best Response
You've already chosen the best response.
2
therefore the new kinetic energy must be equal to 245 Joules.
mayankdevnani
Best Response
You've already chosen the best response.
1
yaa
mayankdevnani
Best Response
You've already chosen the best response.
1
correct!!!
mathslover
Best Response
You've already chosen the best response.
2
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
mathslover
Best Response
You've already chosen the best response.
2
solve for h and you will get h = 12.5 m
mayankdevnani
Best Response
You've already chosen the best response.
1
1/2 m (u^2 + 2gh ) = 245 J ??????????????
mathslover
Best Response
You've already chosen the best response.
2
got it?
mayankdevnani
Best Response
You've already chosen the best response.
1
no!!!!
mayankdevnani
Best Response
You've already chosen the best response.
1
1/2 m (u^2 + 2gh ) = 245 J
this line!!!
mathslover
Best Response
You've already chosen the best response.
2
since v^2 = u^2 + 2gh
therefore..
mayankdevnani
Best Response
You've already chosen the best response.
1
ok
mayankdevnani
Best Response
You've already chosen the best response.
1
thnx.... i got it @mathslover
mathslover
Best Response
You've already chosen the best response.
2
good,...
mayankdevnani
Best Response
You've already chosen the best response.
1
let @03225186213 be answer.... plz wait
03225186213
Best Response
You've already chosen the best response.
0
1/2 mv^2=mgh
490/2=2 (-9.8)h h= -9.8
because it is moving against gravity
mathslover
Best Response
You've already chosen the best response.
2
@03225186213 same I thought BUT it is given in the quest. that g = 9.8 m/s^2
mayankdevnani
Best Response
You've already chosen the best response.
1
yaaa you are correct thnx @mathslover and @03225186213
03225186213
Best Response
You've already chosen the best response.
0
welcome
mayankdevnani
Best Response
You've already chosen the best response.
1
:)