Question

A body of mass 8g moving with a speed of 30m/s is brought to rest in 2.5sec, by a constant regarding force. Calculate the magnitude of the force.

Answer 1

Given:-

mass=8g=0.008kg

speed=30m/s

time=2.5sec

To find:-

magnitude of force=?

$by \: using \: first \: equ \: of \: motion$

$v = u + at$

v=final velocity=0

u=initial velocity=30m/s

t=time=2.5sec

a=acceleration=?

$0 = 30 + a \times 2.5$

$- 30 = 2.5 \times a$

$a = - 30 \div 2.5$

$a = - 12m {s}^{ - 2}$

As we know,

$f = ma$

F=force=?

m=mass=0.008kg

a=acceleration=-12m/s^2

putting the values,

$f = 0.008 \times ( - 12)$

$f = - 0.096N$

so force is 0.096N and the minus sign show the direction of force is opposite to the direction of motion..