Momentum
What are the units for momentum
kgm/s
What are the two ways to solve for impulse?
impulse = Ft
impulse = pf - pi
What is the impulse exerted on person that experiences an 85 N net force over 0.7 seconds?
59.5 kgm/s
Explain an Inelastic collision scenario and give an example. (in the context of momentum conservation)
Any time two or more objects collide and DO stick together. (partially or completely)
True or False: A larger object always has greater momentum.
Correct and explain if false, explain if true.
False, momentum depends on mass AND velocity
True or False: The change in momentum of an object is always equal to the impulse exerted on the object.
True! Not only does the impulse cause the momentum to change, but the size of the impulse is also identical to the amount that the momentum changes
If the momentum of an object stays the same, but the mass has tripled, what must have happened to the velocity?
Velocity must have been cut into a third (divided by 3)
Explain a PERFECTLY elastic collision scenario and give an example.
Any time two or more objects collide and DO NOT stick together. (they don't need to bounce)
Kinetic Energy is conserved.
Similar: same variables, deal with motion.
different: momentum is linear and a vector, kinetic energy is scalar and not always conserved in collisions.
Which impulse is higher? Why?
A. A school bus, going 30 mph, comes to a stop by running into the side of a building.
B. A school bus, going 30 mph, comes to a stop by slowly pressing on the brakes as it approaches a stop sign.
The impulses are the same because the bus in both situations has the same starting and final momentum.
The total momentum of Steven on his bike is 770 kgm/s. What is his mass, if he is riding at 10 m/s?
77 kg
The recoil momentum of a tank initially at rest is (smaller than/greater than/the same as) the momentum of the projectile that it shoots. Choose one and explain your answer.
THE SAME AS.
This is because the tank/projectile system starts with a momentum of zero, so according to the Law of Conservation of Momentum, it should end up with a total momentum of 0. This means the tank has some negative momentum and the projectile has a positive momentum, and these must be the same size to add up to zero.
Velocity was cut in half
You have a ball of clay and a bouncy ball, both with the same mass. The ball of clay sticks to the door, and the bouncy ball bounces back off the door. If they are both thrown at the same speed, which object, if either, has the greater impulse? Explain
The bouncy ball! Momentum changes more when the object changes direction compared to when it just comes to a stop.
A bullet train with a mass of 48,000 kg slows down from 130 m/s to 50 m/s. What is the impulse exerted on the train by the brakes?
-3,840,000 kgm/s
A 400 kg paddle boat moves with a velocity of 6.25 m/s collides head-on with a 200 kg raft that started out moving at -2 m/s to the left. If the boat and the raft stick together what is there final velocity?
3.5 m/s
A piece of clay at rest is exploded into FOUR pieces. The first piece of clay has a momentum of -10 kg m/s to the left. The second piece has a momentum of 2 kg m/s to the right. The third piece goes to the right with a momentum of 11 kgm/s. What is the momentum of the fourth piece, and in what direction does it move?
3 kgm/s, to the left (-3 kgm/s)
If two identical eggs are thrown at the same velocity, one at a wall and one at a curtain, what is the difference in the collision that occurs? Use the words impulse, force, and time properly in your explanation.
The impulse on both eggs is the same, but the force on the "wall" egg is much greater because the time of impact is much less, because the wall does not have as much "give" as the curtain.
Give an example of a safety feature or technique that can be explained using impulse and explain how it works, using the terms impulse, force, and time.
Multiple safety feature works that increase the time of impact (possibly by being soft or cushiony), which then lessens the force due to the impulse being the same with or without the technique/feature.
Two kickballs, red and green, roll into each other and bounce off. The red ball, mass of 1.5 kg, is originally moving at 3 m/s to the right, and it hits the green ball which has a mass of .8 kg was originally moving at -5 m/s to the left. After the bounce, the green ball is moving at 4.38 m/s. How fast was the red kickball going after the bounce.
-2 m/s