Question

a velocity of a body of 10kg increase from 4m/s to 8m/s when a force act on it for 2s . (a)what is the value of force
(b)what is the momentum after the force act​

Answer 1

(a) Since force= mass × acceleration

We need to find Acceleration first which is defined as rate of change of velocity.
i.e

$acceleration = \frac{change \: in \: velocity}{change \: in \: time}$

Using the two values of velocities here,
we have acceleration as,

$\frac{(8 - 4)m {s}^{ - 1} }{2s} \\ = \frac{4 \: m {s}^{ - 2} }{2} \\ = 2m {s}^{ - 2}$

And given value of mass = 10 kg

So the force becomes,

$10 \: kg \times 2m {s}^{ - 2}$
Which is equal to 20 N.



(b)

After the force acts the momentum becomes force × final velocity applied on the body,

So,

$final \: momentum = 10 \: kg \times 8m {s}^{ - 1} \\ = 80 \: kg \: m {s}^{ - 1}$