Question

velocity of an object of mass 50 kg increase from 3 metre second to 12 m second what will the force required for this​

Answer 1

$a = (v1 - v2) \div t \\ a = (12 - 3) \div 1 \\ a = 9mt \: pr \: sec2 \\ f = ma \\ f = 50 \times 9 \\ f = 450n$

Answer 2

The force required is 450. Let the body displace for t sec under the action of this force. So from Newton's 2nd law we know that f=m(v-u)/t.

If you use this formula in this case v= 12 and u=3 and m is 50. Now let us put it all together and we get f= 450/t N. This is the force required.