Question

computer the power required by a man to move a 10 kg mass to change the speed from 10 MS to 20 m s in 5 second

Answer 1

Hello friend,

Here's your answer:
Formula :
P = W/t
=> P = (F × s)/t (Since Work = F × s)
=> P = (m × a × s)/t (Since Force = m × a)
=> P = [m × [(v - u)/t] × s]/t (Since a = (v - u)/t )
=> P = [m × s × (v - u)]/t²
=> P = (ms(v - u))/t²
Now Substituting the values which are
m = 10 kg
u = 10 m/s
v = 20 m/s
t = 5 s.
=> P = (10 × s × (20 - 10))/5²
=> P = (10s × 10)/25
=> P = 100s/25
=> P = 4s -(1)

For finding distance (s) there are two methods.
1) Substituting values in
s = ut + ½at²
2) Substituting values in
v² - u² = 2as
Both give same answer.
Which is s = 75 m.

substituting s value in equation (1):
=> P = 4 × 75 = 300 W.
Therefore Power = 300 W.

Hope my answer helps you. It is ©.

Answer 2

So for this question-
KE.1=1/2×10×10×10
=500J
KE.2=1/2×10×20×20
=2000J

THEN WORK DONE =Change in Kinetic energy
So,W=KE.2-KE.1
=1500J

POWER=WORK/TIME
=1500/5
300J/s

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