Question

A force of 10 N is applied in opposite direction
on a body of mass 5 kg moving at a velocity of
6 ms ) In how many seconds does it come to
rest:
(a) 1
(b) 2
(c)3
(d) 4​

Answer 1

Answer

• ( c ) 3 s

Given

• A force of 10 N is applied in opposite direction  on a body of mass 5 kg moving at a velocity of  6 m/s

To Find

• Time in which body comes rest

Solution

Force , F = - 10 N [ Opposite direction ]

Mass , m = 5 kg

Initial velocity , u = 6 m/s

Final velocity , v = 0 m/s { Finally it comes to rest }

Time , t = ? s

We know that , " Using Newton's second law , Force is defined as product of mass and acceleration "

Now , " Acceleration is defined as rate of change of velocity "

$\implies \sf F=ma\\\\\implies \sf F=m\bigg( \dfrac{v-u}{t} \bigg)\\\\\implies \sf -10=5\times \bigg( \dfrac{0-6}{t} \bigg)\\\\\implies \sf -10=\dfrac{-30}{t}\\\\\implies \sf t=3 \;s$

So , option ( c ) is correct √