Conservation of Momentum

Conservation of Momentum

Multiple Choice

What is needed to change an object's velocity?

• a force

• an impulse

• a vector

Multiple Choice

What does it take to change an object's momentum?

• a force

• an impulse

• a vector

Multiple Choice

For an internal system such as seen in the cannon-cannonball system, before the firing, the system is at rest and the momentum is zero. After the firing, the net momentum or total momentum, is _______.

• more

• less

• still zero

Multiple Choice

Momentum is a

• vector

• scaler

Let's work a problem:

• •A 100 kg cannon fires a 5 kg cannonball at 100 m/s. How fast does the cannon move backwards?

  •Use the GUESS method

  •Given: M1 = 100  M2 = 5 kg   V2 = 100 m/s

  •Unknown:  V1 = ?

  •Equation:  M1 V1 = M2 V2  

  •Substitute:  100 kg x V1 = 5 kg x 100 m/s

  •Solve:  V1 = 5 m/s

Multiple Choice

A .030 kg bullet is fired from a gun with a speed of 350 m/s. If the gun has a mass of 0.9 kg, What is the recoil speed of the gun?

• 11.7 m/s

• 9.0 m/s

• 10.5 m/s

• 10 m/s

Multiple Choice

The recoil speed of a rifle is much less than the exit velocity of a bullet because...

• the rifle experiences a smaller force

• the rifle experiences a smaller change in momentum

• the rifle has a much greater mass

• the rifle does not obey the laws of physics

Multiple Choice

Newton’s second law states that if no net force is exerted on a system, no acceleration occurs. Does it follow that no change in momentum occurs?

• yes

• no

Multiple Choice

Newton’s third law states that the force a cannon exerts on a cannonball is equal and opposite to the force the cannonball exerts on the cannon. Does it follow that the impulse a cannon exerts on a cannonball is equal and opposite to the impulse the cannonball exerts on the cannon?

• yes

• no

Multiple Choice

In an ________ collision, two objects collide without being deformed or generating any heat. Think billiard balls!

• elastic

• inelastic

Multiple Choice

Two carts with mass 75 kg and 100 kg run into each other with speeds of 6 m/s and 8 m/s respectively. If they hook together as they collide, the combined speed of the two carts just after the collision would be:

• -2 m/s

• 3.4 m/s

• 4.6 m/s

• 7.1 m/s

Multiple Choice

Two carts with mass 50 kg and 150 kg respectively run into each other. The first cart is traveling at a velocity of 8 m/s. The second cart was at rest. If they hook together as they collide, the combined speed of the two carts just after the collision would be:

• 2 m/s

• 3.4 m/s

• 4.6 m/s

• -7.1 m/s

Multiple Choice

Two football players with mass 75 kg and 100 kg run directly toward each other with speeds of 6 m/s and 8 m/s respectively. If they grab each other as they collide, the combined speed of the two players just after the collision would be:

• -2 m/s

• 3.4 m/s

• 4.6 m/s

• -7.1 m/s

Multiple Choice

Two skaters begin at rest. Skater 1 has a smaller mass than Skater 2. After they push off each other,...

• Skater 1 experiences a greater change in momentum

• Skater 2 experiences a greater change in momentum

• Skater 1 has a greater velocity than Skater 2

• Skater 1 experiences a greater force

Multiple Choice

A 3,000 kg truck moving at +10 m/s hits a 1,000 kg parked car which moves off at +15 m/s. What is the velocity of the truck?

• 10 m/s
• 0 m/s
• 5 m/s
• 2 m/s

Multiple Choice

The total momentum before a collision is _________ the total momentum after a collision.

• equal to

• less than

• more than

• It depends on the type of collision

Multiple Choice

An 1 kg object moving to the right at 2 m/s collides inelastically with a 1 kg object moving to the left at 2 m/s. The final velocity of both objects will be

• 0 m/s

• 1 m/s

• 2 m/s

• 4 m/s

Multiple Choice

A 1000 kg car is traveling east with a velocity of 10 m/s collides with a 5000 kg northbound truck moving at a velocity of 8 m/s. What is the magnitude and direction of the resultant inelastic collision?

• 41, 231 kg m/s

  south/ southeast

• 41, 231 kg m/s north/northeast

• 45,321 kg m/s north/northeast

• 36, 565 kg m/s

  south/ southeast