[phy]magnitude..impulse...help

1. Final speed, v = 0

Impulse = change of momentum

So, the magnitude of impulse required to stop the automobiles = │mv - mu│ = mu

A: Impulse = (1000)(20) = 20 000 kgms-1

B: Impulse = (500)(10) = 5000 kgms-1

C: Impulse = (500)(20) = 10 000 kgms-1

D: Impulse = (2000)(5) = 10 000 kgms-1

E: Impulse = (4000)(5) = 20 000 kgms-1

F: Impulse = (1000)(10) = 10 000 kgms-1

So, from the largest to the smallest magnitude of impulse,

the correct order is:

A & E > C, D & F > B.


2. Impulse = change of momentum

Ft = mv - mu = -mu

F = -mu / t

As the impact times for each impact are unknown, hence we cannot determine the value of forces to stop the automobiles. Therefore, the order cannot be determined.

#1
impulse = chage in momentum
=the final momentum - the intial momentum
= 0(final velocity is zero) - the initial momentum
=- initial momentum
obseviously, the magnitude required is equal to the initial momentum

by using the formula momentum= velocity x mass

we have A=E > C=D=F > B

#2
For part 2 ,it is undetermined
Impulse = change in momentum
= time x force
time x force= change in momentum
force= change in momentum / time
As we dont know the time for deceleration.
It is impossible to calculate unless it has given the time.