Newtons Third Law of Motion 1 FORCES AND
- Slides: 23
Newton's Third Law of Motion
1. FORCES AND INTERACTIONS n Force is an interaction between one thing and another. n Ex: 2 people pushing each other on skate boards, driving a nail, punching a bag n There is no single isolated force
2. NEWTON'S THIRD LAW OF MOTION n Law 3 - Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first. n Action-reaction pairs never act on same object.
Newton’s Third Law deals with two forces acting on two different objects. Newton’s Third Law pairs of forces always, sometimes, never cancel each other out. The only way for two forces to cancel each other out is for them to beequal and opposite and act on thesame object!
Action & Reaction on Different Masses Consider you and the earth Action: earth pulls you Reaction: you pull earth
You F m =a F=a m Earth
Action: tire pushes on road Reaction: road pushes on tire
Reaction: gases push on rocket Action: rocket pushes on gases
n n Hwk read Review book 82 -86 do pg 100 #4, 5, 8 – 14, 24 - 27, 31 -35. Separate sheet.
rd Newton’s 3 Law n Six minutes http: //www. youtube. com/watch? v=c. P 0 B b 3 WXJ_k&feature=relmfu
The subscript notation: n Convention: Fa, b means “the force acting on a due to b”. n So Fhead, thumb means “the force on the head due to the thumb”. Fhead, thumb
Newton's Third Law says. . . FA , B = - FB , A. Fm, w Fw, m Ff, m Fm, f
Hmmm…. The man leans on the box, the box moves. n Since Fm, b = -Fb, m, why isn’t Fnet = 0 and a = 0 ? Fm, b Fb, m a ? ? ice
Need free body diagram of box only. n Consider only the box as the system! – Fon box = mabox = Fb, m Fm, b Fb, m abox ice
The forces acting on the box are: 1. The force of the man 2. The force of the ice (neg). abox
3. SUMMARY OF NEWTON'S THREE LAWS n Law 1 (Law of Inertia) Every object continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it. n Law 2 n Law 3 - Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.
rd Newton’s 3 law … 6 minutes n http: //www. youtube. com/watch? v=c. P 0 Bb 3 WXJ_k &feature=relmfu n Newton’s 3 Laws 4 min http: //www. youtube. com/watch? v=i. H 48 Lc 7 wq 0 U n n http: //www. youtube. com/watch? v=8 b. Td. Mm. NZm 2 M&list=PLEA 0 D 7 C 501 E 484 B 31&index=8
Review Questions
A bug and a car collide. Which experiences the greater force? (a) bug (b) car (c) neither, they both experience the same magnitude of force
Consider hitting a baseball with a bat. If we call the force applied to the ball by the bat the action force, identify the reaction force. (a) the force applied to the bat by the hands (b) the force applied to the bat by the ball (c) the force the ball carries with it in flight (d) the centrifugal force in the swing
n Two blocks are stacked on the ground. n How many action-reaction pairs of forces are present in this system? a (a) 2 (b) 3 b (c) 4
Solution: Fa, E a b Fb, E Fb, a Fa, b a a b b Fb, g Fg, b FE, a FE, b (c) 4
- Third
- Newton's third law
- Newton's 3 laws of motion
- Newton's first law and second law and third law
- Newton's first law of motion
- Describe newtons third law
- Law of thermodynamics in chemistry
- Newton law
- Newton's second law
- Newtons 3 rd law of motion
- Newtons 3 rd law of motion
- Newtons 3 rd law of motion
- Newton's first law meme
- Newtons 3 rd law of motion
- Newtons 3 rd law of motion
- Newtons 3 rd law of motion
- What is one newton
- Second law of newton
- Example of 2nd law of motion
- Newtons law of motion
- According to the third law of motion action and reaction
- According to the third law of motion, action and reaction
- Newtons first lw
- Newtons aw