3.
a 2,000-kilogram car uses a braking force of 12,000 newtons to stop in 5 seconds.
a. what impulse acts on the car?
b. what is the change in momentum of the car?
c. what is the initial speed of the car?

Explanation:

m = 2,000-kilogram

F = 12,000

t = 5 seconds

a) Impulse (I) = Ft = 12000 × 5

I = 60,000 Ns

b) from Newton's 2nd law

F = m∆v/t

Ft = m∆v

change in momentum (∆p) = 60,000kgm/s

c) ∆v = Ft/m = 60,000/2000 = 30m/s

the initial velocity is 30m/s since final velocity is zero

Momentum …

is a quantity that describes an object's

resistance to stopping (a kind of "moving

inertia"). and is represented by the symbol p which is the product of an object's mass and velocity.

p = m v

is a vector quantity (since velocity is a

vector and mass is a scalar).

Impulse …

is a quantity that describes the effect of a

net force acting on an object (a kind of

"moving force").

is represented by the symbol I

is the product of the average net force

acting on an object and its duration.

I = F Δ t

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement