WarmUp

1

• Warm-Up
• Vehicle A is traveling southeast at 100 km/h,
  and vehicle B is also traveling southeast but at
  80 km/h. Both vehicles have the same mass. Which
  of the following statements about these two
  vehicles is true?
• 1. Vehicle A has greater momentum than
  Vehicle B. 2. Vehicle B has greater momentum
  than Vehicle A. 3. Both vehicles have the same
  velocity. 4. Both vehicles have the same
  momentum.

2

• What does the word
• MOMENTUM
• mean?

3

• "The Pittsburgh Steelers have been gaining
  momentum the past couple of months, and they will
  use that momentum to win the Super Bowl."

4

• In this sports analogy, the Steelers are on the
  move, and it will take a lot of effort from the
  Seahawks to stop them.

5

• Just as if a sports team
• is on the move, it has
• momentum...
• If any object is on
• the move, it has
• momentum.

6

• Momentum
• Mass in Motion.

7

• Momentum
• Mass Velocity
• or
• ? mv

8

• The unit for momentum is
• kg ? m
• s

9

• Momentum is a vector quantity-
• both distance and direction are important.
• Momentum answers must be given not only with
  magnitude, but also with direction.

10

• By looking at the equation,
• ? mv
• we can see that if an object has a large mass
  and/or a large velocity, it has a large momentum.

11

• If a semi truck and a motorcycle are driving down
  the highway at the same velocity, which of the
  two will be more difficult to stop?
• This will be the object with the greater momentum.

12

• But if the semi is already stopped and the
  motorcycle is driving at 60 mi/hr, which has the
  greater momentum then?

13

• OBJECTS AT REST DO NOT HAVE MOMENTUM.

14

• Ball demonstration

15

• 1. Determine the momentum of a
• A) 200-kg horse moving southward at 9 m/s.
• B) 1000-kg car moving northward at 20 m/s.
• C) 40-kg dog moving westward at 3 m/s.

16

• A car possesses 20 000 units of momentum. What
  would be the car's new momentum if ...
• A) its velocity were doubled.
• B) its mass were doubled (by adding more
  passengers and a greater load)
• C) both its velocity were doubled and its mass
  were doubled.

17

• To stop an object with momentum,
• a force must be applied.
• Objects with greater momentum require either a
  greater amount of force to stop them, or a
  greater amount of time.
• Unbalanced forces will change an object's
  momentum.

18

• Impulse
• A change in momentum
• Force time

19

• F t m ?v

20

• A 2 kg cart (1) is pulled with a 2.0N force for
  2 seconds.
• Another 2 kg cart is pulled with a force of 1.0N
  for 4 seconds.
• 1) Which has the greatest acceleration?
• 2) Which has the greater impulse?
• 3) Which has the greater change in momentum?

21

• Mrs. G, who has a mass of 50 kg, is driving in
  her SUV at 25.0 m/s when she has to slam on the
  brakes to avoid a collision. She is restrained
  by the seatbelt, bringing her body to a stop in
  0.50 s.
• 1) What force does the seatbelt exert?

22

• If she was not wearing her seatbelt, she would
  been brought to a stop by the windshield in
  0.001 s.
• 2) What average force would the windshield have
  exerted on her?

23

• A hockey player applies an average force of 100 N
  to a 0.3kg hockey puck for a time of 0.10 s.
• 3) What was the impulse experienced by the hockey
  puck?

24

• 4) If a 10 kg object experiences a 20N force for
  a duration of 0.2 s, what is the momentum change
  of the object?