Question

A toy car of mass 0.15kg accelerates from a speed of 10 cm/s to a speed of 15 cm/s. What is the impulse acting on the car?

Answer 1

v=v2-v1=15-10=5 cm/s

p=mv=0.15•5=0.75 kg•cm/s

Answer 2

Answer : The correct option is, (A) 7.5 mN.s

Explanation :

Impulse : It is defined as the force applied to an object for a certain amount of time.

Formula used :

$I=F\times \Delta t$

As we know that:

$F=m\times \Delta a\\\\\Delta a=\frac{\Delta v}{\Delta t}$

Thus, formula of impulse will be:

$I=m\times \Delta v$

where,

I = impulse  = ?

m = mass = 0.15 kg

$\Delta v$ = change in speed of velocity = $v_{final}-v_{initial}=15cm/s-10cm/s=5cm/s=0.05m/s$     (1 m = 100 cm)

Now put all the given values in the above formula, we get:

$I=(0.15kg)\times (0.05m/s)$

$I=0.0075kg.m/s=0.0075N.s=7.5mN.s$      (1 N.s = 1000 mN.s)

Therefore, the impulse acting on the car is, 7.5 mN.s