Question

a force applied on abody of mass 4kg for 5seconds changes its velocity from 10m\s to 20m\s .Find the power required.

Answer 1

mass: 4kg
time: 5seconds
initial velocity: 10m/s
final velocity: 20m/s

By using first equation of motion;
v= u+at
20= 10+a× 5
20=10+5a
20-10= 5a
10= 5a
10/5= a
a= 2m/s2

Now, Force= mass× acceleration
F= 4× 2
F=8N

Now, by using second equation of motion:
s= u+ 1/2 at2
s= 10+ 1/2 × 2(5)2
s= 20+1/2× 2×25
s= 21/2× 50
s= 21× 25
s= 525m

Work done= force × distance
W= F× s
W= 8× 525
W= 4200J

Now; power= w/t
P= 4200/5
P= 840 W
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