Basics
What is the momentum equation?
rho=mv
What equation defines impulse?
J=FDeltat
Find momentum: 3 kg at 5 m/s. (don't forget units!)
15 kg*m/s
A 2 kg cart at 4 m/s hits a 2 kg cart at rest and sticks. Final velocity?
2 m/s
Why must momentum be split into x and y components?
Because momentum is conserved separately in each direction
If an object explodes at rest, what is total momentum after?
Zero
Which has move momentum? 5 kg at m/s or 2 kg at 6 m/s?
2 kg at 6 m/s
A 10 N force acts for 3s. Find impulse.
30 N*s
Find momentum: 0.5 kg at 12 m/s
6 kg*m/s
A 3 kg cart at 6 m/s hits a 1 kg cart at rest. After, 3 kg cart = 2 m/s. Find other velocity.
12 m/s
A 2 kg object moves east, 3 kg moves north. After collision they stick—what do you solve separately?
Total momentum in x and total momentum in y
A 4 kg object breaks into two pieces. One goes right—what happens to the other?
Moves left
What is the SI unit if impulse?
N*s
If time increases and force stays constant, what happens to impulse?
It increases
A 10 kg object slows from 4 m/s to 0. What is the change in momentum?
-40 kg*m/s
Two objects stick: 4 kg at 5 m/s and 2 kg at -1 m/s. Final velocity?
3 m/s
A 1000 kg car east at 10 m/s + 1000 kg north at 10 m/s stick. Direction?
45° north of east
A gun fires a bullet—why does it recoil?
Conservation of momentum
What happens to momentum if velocity doubles?
Momentum doubles
Why do helmets reduce head injuries?
They increase impact time -> reduce force.
A 2 kg object reverses from 3 m/s to -3 m/s. Find the change in momentum.
-12 kg*m/s
A 1 kg object hits a 2 kg object at rest. After, 2 kg moves at 3 m/s. Find original velocity
6 m/s
A 1500 kg car east 15 m/s hits 1000 kg south 10 m/s (stick).Find final velocity and direction.
10.3 m/s at 24 degrees south of east
A 6 kg object splits into 2 kg moving right at 10 m/s. What direction does the other go?
Left
Why is momentum a vector quantity?
It has both magnitude and direction.
A graph shows force vs. time - what does the area represent?
Impulse
Rank least to most momentum:
A. 4 kg @ 2m/s
B. 2 kg @ 5m/s
C. 1 kg @ 9m/s
A, C, B
A 5 kg object at 2 m/s collides with a 3 kg object at -4 m/s. They stick—find final velocity
A 1200 kg car moving west at 14 m/s collides with a 900 kg car moving north at 10 m/s. The cars stick together after the collision. Solve velocity and direction.
9.08 m/s at 28.18 degrees north of west.
A 8.0 kg object at rest explodes into two pieces. One piece has a mass of 3.0 kg and moves east at 6.0 m/s. Find the velocity of the 5.0 kg piece
3.6 m/s west