Advertisements
Advertisements
Question
How fast should a boy weighting 30 kg run so that his kinetic energy is 375 joule?
Advertisements
Solution
We know that , K.E = `1/2` mv2
375 = `1/2` x 30 x v2
or v2 = `(375 xx 2)/30` = 25 m/s
or v = 5 m/s
APPEARS IN
RELATED QUESTIONS
Write an expression for the work done when a force is acting on an object in the direction of its displacement.
A force acts on a body and displaces it by a distance S in a direction at an angle θ with the direction of the force. What should be the value of θ to get the maximum positive work?
The S.I. unit of energy is .............
In which of the following cases is work being done:
- A boy pushing a heavy rock
- A boy climbing up the stairs
- A coolie standing with a box on his head
- A girl moving on the road.
State two factors on which the work done on a body depends.
A box of weight 150 kgf has gravitational potential energy stored in it equal to 14700 J. Find the height of the box above the ground. (Take g = 9.8 N kg-1)
Define 'joule'.
A bullet is of mass 'm' g and is moving with a velocity 'v' m/s. Find the kinetic energy of the bullet when
(a) The mass is doubled,
(b) The velocity is tripled.
