Momentum and Impulse
Worksheet
1.
Two masses m1 and m2, with m1 < m2, have equal kinetic energy. How do the magnitudes of their
momenta compare?
(a) Not enough information is given. (b) p1 < p2 (c) p1 = p2 (d) p1 > p2
2.
How good are Bumpers?
In a crash test, a car of mass 1.50 x 103 kg collides with a wall and rebounds.
The initial and final velocities of the car are vi = -15.0 m/s and vf = 2.60 m/s,
respectively. If the collision lasts for 0.150 s, find (a) the impulse delivered to
the car due to the collision and (b) the size and direction of the average force
exerted on the car.
3.
Suppose the car doesn’t rebound off the wall, but the time interval of the collision remains at 0.150 s.
An effective bumper crumples on impact reducing the cars speed. In this case, the final velocity of the
car is zero. Find the average force exerted on the car.
4.
How do bumpers reduce injury in car crashes? (Compare the average force in 2 and 3)
5.
When a person is involved in a car accident, why is the likelihood of injury greater in a head-on
collision as opposed to being hit from behind? Answer using the concepts of relative velocity,
momentum, and average force.
6.
Read “Injury in auto-mobile collisions” and answer the following question: How do seatbelts, headrests
and airbags reduce injury in a car crash?