Force and Time in Collisions - Learn

Force and Time in Collisions

Problems of this nature usually consider two equations:

$I=Ft$ and;

$I=\Delta P=mv-mu$

Example 1:

A $20N$ force acts on a stationary RC car of mass $2.5kg$ for $3.0s$

a) Calculate the magnitude of the impulse of the force on the car:

b) Calculate the change in speed the impulse produces:

a) $I=Ft$

$I=20\times 3=60Ns$

b) Impulse = $\Delta p$ , and $\Delta p=mv-mu=m(v-u)$

Therefore; $60=2.5(v-0)$

$v=\cfrac { 60 }{ 2.5 }$

$v=24\cfrac { m }{ s }$

Example 2:

A toy car of mass $2kg$ is at rest. A force acts on it for $4.0s$ , increasing its speed to $8\cfrac { m }{ s }$

a) Find the impulse the force applies:

$I=\Delta p=mv-mu$

$I=\Delta p=(2\times 8)-(2\times 0)$

$I=16Ns$

b) Find the force applied to the car.

$I=Ft$

$16=F\times 4$

$F=\cfrac { 16 }{ 4 }$

$F=4N$