Momentum is the product of mass and velocity of an object.
The symbol for momentum is p.
p(kg*m/s)= m(kg) v(m/s)
EXAMPLE:
A proton has a mass of 1.67 x 10-27 kg travels at a velocity
of 99% that of the speed of light (3.0 x 108 m/s). What is the momentum of the proton?
SOLUTION.
p
= m v
p = (1.67 x 10-27 kg) (.99 x
3.0 x 108 m/s)).
p = 5.0 x 10-19 kg*m/s
When an object is moving, it has momentum. The momentum of the object will change if a force is applied
to it.
The amount of force (F) applied multiplied by the the
amount of time (Δt ) the force is applied to the object is called impulse.
Impulse-Momentum Theorem
FΔt
= Δp OR FΔt =
(mvf - mvi)
PROBLEM:
A 1400 kg car moving westward with a
velocity of 15 m/s collides with a utility pole and is brought to rest in 0.30 s. Find the force exerted on the car during
the collision.
SOLUTION:
Given:
m=1400 kg
vi = 15m/s to the west, vi =
-15 m/s
vf = 0 m/s
Δt =
.30s
F = ?
Solution:
FΔt = (mvf -
mvi)
F = (mvf
- mvi) / Δt
F
= (1400kg) (0m/s) - (1400kg)(-15m/s) / 0.30 s
F = 21000 kg*m/s / 0.30s
F = 7.0 x 104 N to the east
Stopping times and
distances depend on the impulse-momentum theorm.
Force is reduced when the time
interval of an impact is increased.
Click here for more information on momentum.
