Presentation is loading. Please wait.

Presentation is loading. Please wait.

Mommentum. 11/17 1. Why is falling on the grass less dangerous than falling on concrete? 2. Why is it important to follow through when swinging a bat.

Similar presentations


Presentation on theme: "Mommentum. 11/17 1. Why is falling on the grass less dangerous than falling on concrete? 2. Why is it important to follow through when swinging a bat."— Presentation transcript:

1 Mommentum

2 11/17 1. Why is falling on the grass less dangerous than falling on concrete? 2. Why is it important to follow through when swinging a bat or golf club?

3 Grade your self out of 4 using the Justification Rubric

4 Momentum is conserved for all collisions as long as external forces don’t interfere.

5 The concept of inertia was introduced and developed both in terms of objects at rest and objects in motion. In this chapter we are concerned only with the concept of inertia in motion—momentum. Energy – the ability to do work

6

7 A moving object can have a large momentum if it has a large mass, a high speed, or both. 8.1 Momentum

8 Momentum is the mass of an object multiplied by its velocity. momentum = mass × velocity P = M *V momentum = mv When direction is not an important factor, momentum = mass × speed 8.1 Momentum

9 A truck rolling down a hill has more momentum than a roller skate with the same speed. But if the truck is at rest and the roller skate moves, then the skate has more momentum. 8.1 Momentum

10 Conservation of Momentum - the total momentum of an system of interacting bodies remains constant P in = P out

11

12

13 The quantity force × time interval is called impulse. impulse = F × t The greater the impulse exerted on something, the greater will be the change in momentum. impulse = change in momentum Ft = ∆(mv) 8.2 Impulse Changes Momentum

14 When you push with the same force for twice the time, you impart twice the impulse and produce twice the change in momentum. 8.2 Impulse Changes Momentum

15 The force of impact on a golf ball varies throughout the duration of impact. 8.2 Impulse Changes Momentum

16 If the change in momentum occurs over a long time, the force of impact is small. 8.2 Impulse Changes Momentum

17 If the change in momentum occurs over a short time, the force of impact is large. 8.2 Impulse Changes Momentum

18 When you extend the time, you reduce the force. A padded dashboard in a car is safer than a rigid metal one. Airbags save lives. To catch a fast-moving ball, extend your hand forward and move it backward after making contact with the ball. 8.2 Impulse Changes Momentum

19 The impulse provided by a boxer’s jaw counteracts the momentum of the punch. a. The boxer moves away from the punch. b. The boxer moves toward the punch. Ouch! 8.2 Impulse Changes Momentum

20 think! When a dish falls, will the impulse be less if it lands on a carpet than if it lands on a hard floor? 8.2 Impulse Changes Momentum

21 1. Why can Muhammad exert a greater punching force with his bare fist than he can while wearing a boxing glove? 2. What is the difference between impulse and momentum? 3. Can you think of a case where a roller-skate would have the same momentum of a car?

22 think! Can you think of a case where a roller skate and a truck would have the same momentum? Answer: The roller skate and truck can have the same momentum if the speed of the roller skate is much greater than the speed of the truck. For example, a 1000-kg truck backing out of a driveway at 0.01 m/s has the same momentum as a 1-kg skate going 10 m/s. Both have momentum = 10 kgm/s. 8.1 Momentum

23 11/18 1. Why can Muhammad exert a greater force hitting a concrete wall than hitting a stack of hay? 2. What is the difference between impulse and momentum? Agenda : momentum stations lab Choose a station to explain

24 11/19 Which station do you think you can describe the best? Does your station show conservation of momentum or impulse as change in momentum? Explain your station to a classmate as best you can.

25 If the flower pot falls from a shelf onto your head, you may be in trouble. If it bounces from your head, you may be in more serious trouble because impulses are greater when an object bounces. The increased impulse is supplied by your head if the pot bounces. 8.3 Bouncing

26 Cassy imparts a large impulse to the bricks in a short time and produces considerable force. Her hand bounces back, yielding as much as twice the impulse to the bricks. 8.3 Bouncing

27 The curved blades of the Pelton Wheel cause water to bounce and make a U-turn, producing a large impulse that turns the wheel. 8.3 Bouncing

28 11/20 Warm up Use your notes to see if you can figure out the solutions. 1.A bowling ball with a mass of 6 kg experiences a change in velocity of 2 m/s. What is the change in momentum? 2. A child on a sled with a mass of 10 kg experiences a change in momentum of 70 kg*m/s. What is its change in velocity? Agenda : momentum practice » Work on momentum brochures

29 The momentum before firing is zero. After firing, the net momentum is still zero because the momentum of the cannon is equal and opposite to the momentum of the cannonball. 8.4 Conservation of Momentum

30 The force on the cannonball inside the cannon barrel is equal and opposite to the force causing the cannon to recoil. The action and reaction forces are internal to the system so they don’t change the momentum of the cannon-cannonball system. Before the firing, the momentum is zero. After the firing, the net momentum is still zero. Net momentum is neither gained nor lost. 8.4 Conservation of Momentum

31 11/20 Next assignment. Choose a station. Write about how this station shows conservation of momentum. P= mv. Conservation of momentum M 1 V 1 = M 2 V 2

32 Momentum has both direction and magnitude. It is a vector quantity. The cannonball gains momentum and the recoiling cannon gains momentum in the opposite direction. The cannon-cannonball system gains none. The momenta of the cannonball and the cannon are equal in magnitude and opposite in direction. No net force acts on the system so there is no net impulse on the system and there is no net change in the momentum. 8.4 Conservation of Momentum

33 What is the difference between an ellastic collision and an inelastic collision fendt.de/ph14e/collision.htm

34 Elastic collision – no lost of energy after a collision Inelastic collision – energy is lost after a collision

35 The law of conservation of momentum describes the momentum of a system: If a system undergoes changes wherein all forces are internal, the net momentum of the system before and after the event is the same. Examples are: atomic nuclei undergoing radioactive decay, cars colliding, and stars exploding. 8.4 Conservation of Momentum

36 Why does conservation of momentum matter? Cern rap song ojtM

37 Give jacko slide – see notes Work on momentum problems – except for 7 th hour

38 Definition of conservation of momentum Conservation of momentum The total momentum in the beginning is the same as the total momentum in the end

39 a.A moving ball strikes a ball at rest. b.Two moving balls collide head-on. c.Two balls moving in the same direction collide. 8.5 Collisions

40 In an inelastic collision between two freight cars, the momentum of the freight car on the left is shared with the freight car on the right. 8.5 Collisions

41 The freight cars are of equal mass m, and one car moves at 4 m/s toward the other car that is at rest. net momentum before collision = net momentum after collision (net mv) before = (net mv) after (m)(4 m/s) + (m)(0 m/s) = (2m)(v after ) 8.5 Collisions

42 do the math! Consider a 6-kg fish that swims toward and swallows a 2-kg fish that is at rest. If the larger fish swims at 1 m/s, what is its velocity immediately after lunch? 8.5 Collisions

43 do the math! Consider a 6-kg fish that swims toward and swallows a 2-kg fish that is at rest. If the larger fish swims at 1 m/s, what is its velocity immediately after lunch? Momentum is conserved from the instant before lunch until the instant after (in so brief an interval, water resistance does not have time to change the momentum). 8.5 Collisions

44 do the math! 8.5 Collisions

45 Momentum is conserved for the high-speed elementary particles, as shown by the tracks they leave in a bubble chamber. 8.6 Momentum Vectors

46 A change in momentum is caused by exerting a force over time. Show how this is derived from Newtons second law (f=ma).

47 10/29 What do problems have in common? In terms of momentum transfer, what is the difference between an elastic collision and an inelastic collision? ey/phys1/lectures/lecture7/momentum_cons ervation.html ey/phys1/lectures/lecture7/momentum_cons ervation.html

48 Monday 11/1 Momentum quiz Wednesday Give an example of a momentun transfer that happened last weekend Practice questions

49 1. In skate bowling why does the cart you are sitting on not move as much as the ball? Create a diagram and explanation that shows how this show conservation of momentum? 2. Use impulse to show the momentum change in each car. During the car pull on station 6.

50 Compare the elastic and inelastic collision cars in terms of momentum transfer. Which case did all the momentum transfer, how do you know? How do you know that momentum is being transferred through the middle ball to the opposite ball?

51 A.1 kg cue billard ball is traveling at 4 m/s when it collides with a stationary ball of the same mass. The final speed of the cue ball is 3 m/s. How fast is the ball that got hit?

52 10/31 What happens to the momentum of an object if its mass is doubled? For station five describe how the number of balls released is showing conservation of momentum. Notebook check: dates from 10/22 today or tomorrow Quiz tomorrow – review sheet available Brochures due tomorrow

53 When you threw the bowling ball for skate bowling, compare the ball to you in the following a.Velocity b.Mass c.Momentum d.Force e.impulse Are you ready for the quiz? Notebook check from 10/22

54

55 An object with a mass of 5 kg experiences a change in velocity of 12 m/s. What is the change in momentum? A bowling ball has the mass of 5 kg and its momentum is 25 kg m/s, what is it’s velocity? A 40 kg child running at 5 m/s jumps on a stationary cart that weighs 10 kg, what is the final velocity?

56 1.When the speed of an object is doubled, its momentum a.remains unchanged in accord with the conservation of momentum. b.doubles. c.quadruples. d.decreases. Assessment Questions

57 1.When the speed of an object is doubled, its momentum a.remains unchanged in accord with the conservation of momentum. b.doubles. c.quadruples. d.decreases. Answer: B Assessment Questions

58 2.The impulse-momentum relationship is a direct result of Newton’s a.first law. b.second law. c.third law. d.law of gravity. Assessment Questions

59 2.The impulse-momentum relationship is a direct result of Newton’s a.first law. b.second law. c.third law. d.law of gravity. Answer: B Assessment Questions

60 3.When a falling object bounces, as it hits the ground its change in momentum and the impulse on it is a.less than for stopping. b.greater than for stopping. c.the same as it is for stopping. d.the same as it was when dropped. Assessment Questions

61 3.When a falling object bounces, as it hits the ground its change in momentum and the impulse on it is a.less than for stopping. b.greater than for stopping. c.the same as it is for stopping. d.the same as it was when dropped. Answer: B Assessment Questions

62 4.On roller blades you horizontally toss a ball away from you. The mass of the ball is one tenth your mass. Compared with the speed you give to the ball, your recoil speed will ideally be a.one tenth as much. b.the same. c.ten times as much. d.100 times as much. Assessment Questions

63 4.On roller blades you horizontally toss a ball away from you. The mass of the ball is one tenth your mass. Compared with the speed you give to the ball, your recoil speed will ideally be a.one tenth as much. b.the same. c.ten times as much. d.100 times as much. Answer: A Assessment Questions

64 5.A big fish swims upon and swallows a small fish at rest. After lunch, the big fish has less a.speed. b.momentum. c.both of these d.none of these Assessment Questions

65 5.A big fish swims upon and swallows a small fish at rest. After lunch, the big fish has less a.speed. b.momentum. c.both of these d.none of these Answer: A Assessment Questions

66 6.A falling firecracker bursts into two pieces. Compared with the momentum of the firecracker when it bursts, the two pieces a.combined have the same momentum. b.each have half as much momentum. c.have more momentum. d.may or may not have more momentum. Assessment Questions

67 6.A falling firecracker bursts into two pieces. Compared with the momentum of the firecracker when it bursts, the two pieces a.combined have the same momentum. b.each have half as much momentum. c.have more momentum. d.may or may not have more momentum. Answer: A Assessment Questions

68 P = VT I = Δp


Download ppt "Mommentum. 11/17 1. Why is falling on the grass less dangerous than falling on concrete? 2. Why is it important to follow through when swinging a bat."

Similar presentations


Ads by Google