Question

How much force would is required to stop a 1200kg car in 2 seconds if the car is traveling at 22 m/s

Answer 1

Force required = F = ?

mass of the car = m = 1200 kg

initial velocity of the car = Vi = 10 m/sec

final velocity of the car = 0

time required to stop the car = t = 20 sec

Using Newton`s 2nd law of motion;

F = ma ………………………(1)

as a = Vf - Vi / t , put this value in equation (1)

F = m ( Vf - Vi /t ) ………………(2)

F = 1200 ( 0 - 10 /20) = - 600 N

here Negative sign shows that external force is acting in opposite direction of the motion to bring it to rest.

we can also calculate this force by using the relation

Rate of change of momentum = net force acting on the object …………(3)

m Vf - m Vi / t = net force acting on the object

m (Vf - Vi / t) = F

1200 ( 0 - 10 /20) = - 600 N = F

so, net force acting on the object =F = - 600 N