physics hw help

Question

The change in momentum (and impulse) are still 3000 N*s. Safety devices (like airbags, seatbelts and crumple zones) cause crashes to take more time to occur. Now the crash takes 1.5 seconds. How much force is exerted on you in this case?

a)3000 N

b)2000 N

c)15000 N

d)6000 N

Answer 1

In a collision/explosion, there is a momentum transfer and total momentum of the joint system remains conserved so long as there is no external force. Here, the change in momentum is 3000 N.s. Based on Newton's Second Law

F = m x a where we can replace acceleration by Change in Velocity divided by change in time(elapsed time)

Then,

F = m Δ V / Δ t ==> m Δ V is indeed the very change in momentum (mv) delta just makes it "change"

Then, Force = Impulse/Time

F = 3000 N.s / 1.5s ( Unit analysis also gives Newtons, hence Force dimension as seconds cancel one another )

F = 2000N