Equations to Remember
Essential Vocab
Typical Questions
Wild Card
100
What is the equation we use to solve for velocity in any collision?
p_1+p_2=p_1'+p_2'
100
What is a totally inelastic collision?
Object stick together with the same final velocity and kinetic energy is not conserved.
100
A 0.5 kg cart moving at 5 m/s collides with a 1.0 kg cart moving at -1 m/s. The two carts stick together and move at a velocity of 1 m/s after the collision. What was the center of mass velocity before the collision?
v_"cm"=1" m/s"
100
How do each of the following change in an inelastic collision?
Total Momentum
Total Mechanical Energy
Center of Mass Velocity
Total Momentum: stays constant
Total Mechanical Energy: decreases
Center of Mass Velocity: stays constant
200
How do you calculate the energy dissipated by a system?
W=DeltaE=E_"final"-E_"initial"
200
When does a system include elastic potential energy?
When it includes a stretched or compressed spring.
200
A 10 kg dog runs into a 5 kg cat at rest. The dog exerts a force of 2 N on the cat and after the collision the car has 3 times the velocity of the dog.
What is the magnitude of the force exerted on the dog?
2 N
200
What two principles would you apply in order to solve this question?
"Cart 1 of mass m, moving at a speed of v, collides with Cart 2 of mass 2m, at rest, on a frictionless surface. The two carts stick together and then move up a frictionless ramp. What maximum height do the carts reach on the ramp?"
1. Conservation of momentum FIRST for the final velocity after the collision.
2. Then conservation of energy to relate the velocity of the system to the final height up the ramp.
300
What do we compare when trying to identify if a collision is elastic or inelastic?
The difference in velocity before and after the collision:
Abs(v_1-v_2) " compared with " Abs(v_1'-v_2')
300
What must be true about the total kinetic energy and difference in velocity of two carts after a super-elastic collision?
The total kinetic energy increases and the difference in velocity increases:
Abs(v_1-v_2) < Abs(v_1'-v_2')
300
How would you find the change in velocity of an object from the graph below?
1. Find the area under the graph to find the impulse.
2. Divide by the mass to relate the impulse to the change in speed
p=mv, "so " Deltap=mDeltav
300
How would you solve for the tension force in this system?
1. Draw the FBD diagram for each mass (tensions must be equal)
2. Solve for the acceleration of the system using the line-method and Newton's 2nd Law
2. Apply Newton's 2nd Law to one of the masses to solve for the internal tension