1 10 pt 15 pt 20 pt 25 pt 5 pt 10 pt 15 pt 20 pt 25 pt 5 pt 10 pt 15 pt 20 pt 25 pt 5 pt 10 pt 15 pt 20 pt 25 pt 5 pt 10 pt 15 pt 20 pt 25 pt 5 pt Momentum ImpulseCollisions Conservation of Momentum Physics Is Phun!

2 How do you calculate the momentum of an object?

3 Momentum = Mass x Velocity

4 True or False: Momentum is a vector quantity.

5 True

6 What is the momentum of a kg object moving at a velocity of 14 m/s?

7 Momentum = Mass x Velocity p = mv = (0.520 kg)(14 m/s) p = 7.28 kg m/sec

8 Of the object’s listed, select the one with the greatest momentum. A) a.22-caliber bullet fired from a rifle B) a bus speeding along a highway C)a sprinter running the 100-yard dash D)the Earth in its orbit E)not enough info to answer

9 Of the object’s listed, select the one with the greatest momentum. A) a.22-caliber bullet fired from a rifle B) a bus speeding along a highway C)a sprinter running the 100-yard dash D)the Earth in its orbit E)not enough info to answer

10 What is the total momentum of the following situation? Assume there is no friction. 2 kg 1.5 m/s0.8 m/s 3 kg

11 What is the total momentum of the following situation? Assume there is no friction. 2 kg 1.5 m/s0.8 m/s 3 kg Momentum of LH-cart = (2 kg)(1.5 m/s) = + 3 kg m/sec Momentum of RH-cart = (3 kg)(- 0.8 m/s) = kg m/sec Total Momentum = + 3 kg m/sec – 2.4 kg m/sec = 0.6 kg m/sec

12 An impulse is equal to which of the following? A) force times distance B) energy C) change in kinetic energy D) change in momentum E) none of these

13 An impulse is equal to which of the following? A) force times distance B) energy C) change in kinetic energy D) change in momentum E) none of these

14 If a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact?

15 If a boxer wishes to reduce the force of impact from an incoming punch, what should they do to the time of impact? Increase the time of impact

16 What is the change in momentum (impulse) of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds?

17 What is the change in momentum (impulse) of a soccer ball that is kicked with a force of 75-N over a time of 0.18 seconds? Change in momentum = impulse = F t F t = (75 N)(0.18 sec) F t = 13.5 N sec

18 A bus and a bug are traveling towards one another when they collide head- on. Which one experiences the greater impulse? A) the bus B) the bug C) they both experience the same impulse D) not enough info

19 A bus and bug are traveling towards one another when they collide head-on. Which one experiences the greater impulse? A) the bus B) the bug C) they both experience the same impulse D) not enough info

20 A 1,000 kg rocket is launched from rest to a speed of 2500 m/sec in a time of 2.5 minutes. What was the average force (in Newtons) exerted on the rocket?

21 Change in momentum = Impulse m v = F t ==> F = m v / t F = (1000 kg)(2500 m/sec)/(150 sec) F = 16,667 Newtons A 1,000 kg rocket is launched from rest to a speed of 2500 m/sec in a time of 2.5 minutes. What was the average force (in Newtons) exerted on the rocket?

22 True or False: Momentum is conserved in every kind of collision.

23 True True or False: Momentum is conserved in every kind of collision.

24 Which kind of collision conserves both momentum and kinetic energy? A) elastic B) inelastic C) both D) neither-only momentum is conserved

25 Which kind of collision conserves both momentum and kinetic energy? A) elastic B) inelastic C) both D) neither-only momentum is conserved

26 Why is it safer to stop an out-of- control car by running into a pond versus hitting a concrete wall?

27 Why is it safer to stop an out-of- control car by running into a pond versus hitting a concrete wall? By running into the pond, the time it takes the car to slow down to a stop is lengthened. Therefore the stopping force is decreased.

28 Why is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)?

29 A bouncing collision is more damaging because the change in velocity, and therefore the change in momentum, is greater. This leads to a larger force. Why is it that a bouncing collision is more damaging than a sticking collision (assuming the same time of impact in each case)?

30 A 0.25 kg softball is hit with a bat. The incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is sec, what was the force of impact?

31 Impulse = Change in Momentum F t = m  v ==> F = m  v / t F = (0.25 kg)(45 m/sec)/(0.078 sec) F = Newtons A 0.25 kg softball is hit with a bat. The incoming velocity of the ball is +25 m/sec and the outgoing velocity is - 20 m/sec. If the time of contact is sec, what was the force of impact?

32 When an asteroid collides with the moon, the moon drastically changes the momentum of the asteroid. By how much does the Moon change its momentum?

33 Precisely the same amount When an asteroid collides with the moon, the moon drastically changes the momentum of the asteroid. By how much does the Moon change its momentum?

34 A firecracker is sitting on the ground when it is lit. After the explosion, what is the total momentum of the pieces flying apart?

35 A firecracker is sitting on the ground when it is lit. After the explosion, what is the total momentum of the pieces flying apart? Zero, because the momentum of the firecracker before the explosion was zero, and momentum must be conserved.

36 A bullet is fired from a heavy rifle. Two questions: Which one experiences a greater change in momentum? Which one experiences a greater change in velocity?

37 A bullet is fired from a heavy rifle. Two questions: Which one experiences a greater change in momentum? Neither, it’s the same Which one experiences a greater change in velocity? The bullet.

38 Two billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision? Bonk! #1 #2 A B C

39 Two billiard balls collide elastically on a table as shown below. Which picture best represents the motion of ball #2 after the collision? Bonk! #1 #2 A B C

40 Two carts collide as shown below and stick together. What is the velocity of the carts after they’ve collided? Assume there is no friction. 3 kg 6 m/s4 m/s 2 kg

41 Two carts collide as shown below and stick together. What is the velocity of the carts after they’ve collided? Assume there is no friction.. 3 kg 6 m/s4 m/s 2 kg Momentum of LH-cart = (3 kg)(6 m/s) = +18 kg m/s Momentum of RH-cart = (2 kg)(-4 m/s) = -8 kg m/s Total Momentum = +10 kg m/s After collision ==> 10 kg m/s = (5 kg)v v = (10 kg m/s)/(5 kg) = +2 m/sec (to the right)

42 How many triangles are there in the following figure?

43 35

44 Spock would often raise his right hand with the fingers splayed apart and say… “Live long and _________.” Also, what was his “race?”

45 “Live long and prosper.” And He was a Vulcan

46 What team did arguably the best baseball player of all time play for before the NY Yankees?

47 George Herman (the Babe) Ruth

48 What California gold-rush entrepreneur used his knowledge of bouncing collisions to design a nearly 90% efficient water wheel?

49 Lester A. Pelton, inventor of the Pelton water wheel

50 Who is the head coach of Mr. Bruce’s favorite college football team? Hint: Until 2009, they were almost unbeatable!

51 USC – Lane Kiffin