Formula's & Concepts
Momentum, as a physical value, is calculated using this equation.
What is (mass)(velocity)?
This law states that momentum is always conserved in either and elastic or inelastic collision.
What is the Law of Conservation of Momentum?
Which has the greater momentum: a 500,000 g Fiat traveling at 17 m/s, or a 2500 kg SUV traveling at 3.5 m/s?
The 2500 kg SUV
Kinetic Energy is conserved in this type of collision.
What is an Elastic Collision?
The area under the curve of a Force vs. time graph
What is Impulse?
Calculated using the following equation: (mass)x(change in velocity)
What is the Impulse (Change in Momentum) of an object?
What has more momentum; an idle semi-truck, or a bird in flight?
Bird in flight
A ball with a mass of 0.25 kg and a speed of 10 m/s collides perpendicularly with a wall and bounces off with a speed of 2 m/s in the opposite direction. What is the magnitude of the impulse acting on the ball?
Impulse = m(vf-v0) = -3 (N)x(s)
Therefore, Magnitude of Impulse = 3 (N)x(s)
A 4 kg object traveling at 4 m/s on a frictionless horizontal surface collides head-on with and sticks to a 3 kg object initially at rest. Will kinetic energy be conserved in this situation? What is the final velocity of the system?
No, Kinetic Energy will not be conserved because of the inelastic collision.
vf = 2.28 m/s ~ 2 m/s
A 3.0 kg lump of clay is sliding to the right on a frictionless surface with speed 5 m/s. It collides head-on and sticks to a 1.5 kg metal sphere that is sliding to the left with speed 9 m/s. What is the kinetic energy of the system after the collision?
KE = .25 J
The two units for an objects Change in Momentum (Impulse).
What are; (kg)x(m/s) and (N)x(s)
Block A and Block B move toward each other on a level, frictionless track. Block A has mass m and velocity +v. Block B has mass 3m and velocity -2v. The blocks collide, and during the collision the magnitude of the net force exerted on block A is F. What is the magnitude of the net force exerted on Block B, and why does it have that value?
The magnitude of the net force exerted on Block B is F. This is due to Newton's 3rd Law of Motion.
How long must a net force of 75 N act on a 40 kg object initially at rest, in order for the object to reach a velocity of 15 m/s?
Time = 8 seconds
An arrow is shot through an apple. If the 0.1 kg arrow changes speed by 14 m/s during the collision and the apple goes from rest to a speed of 4 m/s during the collision, then the mass of the apple must be…
Mass of Apple = .35 kg
A 20.0 kg block is initially sliding across a rough surface with a velocity of 8.0 m/s. If the coefficient of friction between the block and surface is 0.21, what is the change in momentum of the block after 3.88 seconds? Approximately, what is the blocks final velocity?
Impulse(Change in Momentum) = -159.86 (N)x(s)
~ -160 (N)x(s)
vf = .0068 m/s ~ 0.0 m/s
Since the overall Change in Momentum will remain constant during the crash, increasing _____ will result in a decrease in Force felt by the system.
What is time of collision?
An astronaut is stranded outside of the ISS because their maneuvering pack has malfunctioned and their cable his snapped. All they have with them is a brand new $5,000 camera. What must the astronaut do in order to make it back to the ISS before they run out of oxygen?
Throw the camera is some direction away from the ISS.
What impulse is needed to change the speed of a 10.0 kg body from 20.0 m/s to 12.0 m/s in a time of 5.0 s? What force is needed to do this? Watch SigFigs!!
Impulse = -8.0 x101 (N)x(s)
Force = -16 N
A 1250 kg car moving south at 22 m/s collides with a 850 kg car moving west at 16 m/s. These two cars stick together after the collision. What is the magnitude (NO DIRECTION) of their velocity after the collision?
pf = 30,679 (N)x(s) ~ 31,000 (N)x(s)
A freight car with a mass of 6.0 x104 kg is rolling along a level track at 0.40 m/s, dragging a chain behind it.
A) If the largest force that could be applied to the chain is 320.0 N, how long would it take to stop the car?
B) How far would the car move before it could be stopped?
A) Time = 75 seconds
B) Distance = 15 meters
m1v1 + m2v2 = (m1+m2)vf
What is the Law of Conservation of Momentum for an Inelastic Collision?
Two identical blocks are connected to the opposite ends of a compressed spring. The blocks initially slide together on a frictionless surface with velocity v to the right. The spring is then released by remote control. At some later instant, the left block is moving at v/2 to the left, and the other block is moving to the right. What is the speed of the other block and the speed of the center of mass of the system at that instant?
Speed of Other Block = (3v)/2
Speed of Center of Mass = v
A 0.060 kg rifle bullet leaves the muzzle with a velocity of 6.0 x102 m/s. The 3.0 kg rifle is held firmly by a 60.0 kg man. With what velocity will the man and rifle recoil?
-0.57 m/s, (0.57 m/s in direction opposite bullet)
A hockey player of mass 82 kg is traveling north with a velocity of 4.1 m/s. He collides with a 76 kg player traveling east at 3.4 m/s. If the two players "lock together" momentarily, how fast will they be moving, and in what direction?
vf = 2.7 m/s, 37.5o E of N
vf = 2.7 m/s, 52.5o N of E
Block A of mass 3.0 kg is released from rest at the top of a 4.6 m long plane inclined at an angle of 20o. At the bottom of the ramp, it slides on a horizontal surface. After sliding on the horizontal surface, Block A hits and sticks to Block B, which is at rest and has mass 4.0 kg. Assume friction is negligible. The speed of the blocks after the collision is...