Question

Calculate the impulse necessary to stop a 1500kg of car travelling at 90kmph

Answer 1

converting 90 kmph to m/s

90*5/18 = 25m/s

mass of the car, M = 1500 kg

Initial velocity, u = 25 m/s (90kmph to m/s)

Final velocity, v = 0 m/s

We know that impulse is change in momentum, which is

I = p2 – p1

= Mv – Mu

= 1500*0 – 1500*25

= -37500 N

Answer 2

GIVEN :-

• Mass of the car = 1500 kg
• Initial speed of car = 1900 kmph

TO FIND :-

• Impulse required to stop the moving car

SOLUTION :-

We have ,

• m = 1500 kg
• u = 90kmph = 25 m/s
• v = 0 m/s

$\large {\underline {\boxed {\bigstar {\red{ \sf{ \: 1kmph = \frac{5}{18} \: m {s}^{ - 1}}}}}}}$

$\implies \sf \: 90 \: kmph = 90 \times \frac{5}{18} \: m {s}^{ - 1} \\ \\ \implies \sf \: 90 \: kmph = 25 \: m {s}^{ - 1}$

Relation between momentum and impulse is given by,

$\implies \sf \: I = P_2 - P_1\\ \\ \implies \: \large {\underline {\boxed {\bigstar {\red {\sf{ \: I = mv - mu}}}}}}$

$\implies \sf \: I = m(v - u) \\ \\ \implies \sf \: I = 1500(0 - 25) \\ \\ \implies \sf \: I = 1500( - 25) \\ \\ \implies {\underline {\boxed {\blue{\sf {\: I = - 37500 \: kg.m {s}^{ - 1} }}}}}$

∴ The impulse required to stop the moving car of mass 1500kg moving with speed 90kmph is -37500 kgms⁻¹

ADDITIONAL INFO :-

◉ Impulse is a vector quantity and SI unit of impulse is dimensionall same as momentum i.e , Kgms⁻¹

◉ Impulse applied is equal to the change in momentum of a body