Question

The velocity of a body of mass 5 kg changes
from 30 m s-l to 40 ms-' due to a constant
force in 4 s. Work done is

(1) 1.75 kJ
(2) 17.5 kJ
(3) 175 J
(4) 17.5 J
​

Answer 1

Answer:

17.5KJ is the correct answer

Answer 2

m= 5 kg , u = 30 m/s, v= 40 m/s, t= 4 s

a= v-u/t = 40 - 30 /4 = 10/4 = 2.5m per second square.

S (distance) = ut + 1/2 at square

= 140 m

Force = ma= 5*2.5=12.5 N

work done = force * distance

= 12.5 * 140

=1750 J

I kJ = 1000 J

So, 1750/1000

= 1.75 kJ

Hence , The correct alternative is (1) 1.75kJ.