Question 32:
The velocity of a body of mass 10 kg increases from 4 m/s to 8 m/s when a force acts on it for 2 s.
(a) What is the momentum before the force acts ?
(b) What is the momentum after the force acts ?
(c) What is the gain in momentum per second ?
(d) What is the value of the force ?
Lakhmir Singh Physics Class 9
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one second one minute is equal to 60 seconds The 62nd is all the 20 minutes contain a 2016 is a 1 hour and the 60 seconds is a one second
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it is given that, mass of body, m = 10kg
initial velocity, u = 4m/s
final velocity , v = 8 m/s
time taken to change the velocity, t = 2s
(a) momentum before the force acts, L = mu
= 10kg × 4m/s = 40kgm/s
(b) momentum after the force acts, L' = mv
= 10kg × 8m/s = 80kgm/s
(c) gain in momentum per second = change in momentum/time
= (final momentum - initial momentum)/time
= (80 Kgm/s - 40kgm/s)/2w
= 20kgm/s²
(d) force = change in momentum per second
= (final momentum - initial momentum)/time
= (80kgm/s - 40kgm/s)/2s
= 20kgm/s² = 20N [ as we know, 1 Kgm/s² = 1N]
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