1. Newton’s Third Law of Motion
A situation to ponder…
Consider a high-speed bus colliding head-on with an innocent bug. The force of impact splatters the unfortunate bug all over the windshield.
Put the correct answer here including the letter designation.
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2. Which is greater, the force on the bug or the force on the bus?
A situation to ponder…
CHECK YOUR NEIGHBOR
Which is greater, the force on the bug or the force on the bus?
A. Bug.
Bus.
Both are the same.
Cannot say.
C. Both are the same.
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3. Newton’s Third Law of Motion
A situation to ponder…
When Chuck Norris does a pushup, he's pushing the Earth down.
True
False
Put the correct answer here including the letter designation.
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4. Newton’s Third Law of Motion
CHECK YOUR NEIGHBOR
Two “people” of equal mass on slippery ice push off from each other. Will both move at the same speed in opposite directions?
A. Yes.
Yes, but only if both they push equally.
No.
No, because one of them is Chuck Norris and the rules of physics do not apply to him.
A. Yes.
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5. Newton’s Third Law of Motion
CHECK YOUR NEIGHBOR
How hard must the hand be pulling up in order for the scale to read 5 N?
A. Yes.
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6. What does the scale read?
Newton’s Third Law of Motion
CHECK YOUR ANSWER
What does the scale read?
A. Yes.
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7. You would have the largest mass of gold if it weighed 10 N on…
Newton’s Third Law of Motion
CHECK YOUR NEIGHBOR
You would have the largest mass of gold if it weighed 10 N on…
Jupiter
Mercury
Pluto
A. Yes.
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8. Newton’s Third Law of Motion
CHECK YOUR NEIGHBOR
If all moving things (trucks, trains, cars, cats, Chuck Norris, busses, rickshaws, bicycles ridden by circus bears) on the planet moved East, the day would get
Slightly longer
Slightly shorter
all of the above
A. Yes.
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9. Guy vs Tree
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10. Guy vs Guy
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11. Guy vs Chuck Norris ∞
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12. Newton’s Third Law of Motion
CHECK YOUR NEIGHBOR
A ping pong ball launcher is fired. Compared to the force on the ball, the force is….  
Greater on the ball
Greater on the launcher
The same on both
Bummer he got fired. He will have to go on welfare. Good thing a democrat is in office.
A. Yes.
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13. Calculate the acceleration of the cages
0.2kg
100 Kg
7000 Kg
Mu = 0
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14. Calculate the tension in the ropes
FT2
FT1
2500 N
0.2kg
100 Kg
7000 Kg
Mu = 0
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15. What makes an action-reaction pair?
Act on diff objects (Steve the Horse story)
If A acts on B, then B acts on A
Must be acting at the same time
Forces depend on each other
Ex: pushing book up w hand = FN increases but weight doesn’t so they don’t depend on each other
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16. Action reaction
There is a yogi (in lotus pose) on his recycled yoga mat when a butterfly lands on his shoulder.
The butterfly feels the force of gravity pulling her down. What is the reaction force to that?
A) The yogi’s shoulder pushing up
B) The butterfly pulling up on the Earth
C) Air pushing up on the butterfly
D) The force of namaste touching everything in the universe
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17. Other action reaction
There are 4 boxes. They are being pushed on from the left (red arrow). What is the reaction force to the pink arrow?
A) F3,4
B) F4,3
C) F3,2
D) F4,3+2+1 1 2 3 4
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18. Answers Slide 2 = C. both are the same b/c 2nd law Slide 4 = false
3rd law says they both push/pull on each other
Slide 5 = A. yes
They have equal mass so the same force will result in the same acceleration
Slide 6 = 5 N
Slide 7 = 5 N
3rd law says that you need equal and opposite forces. Also, if nothing were pulling backwards, the scale would read zero. So its just like the question on slide 6
Slide 8 = C. Pluto
If you can get a scale to read 10 N on a planet with such little gravity as Pluto, then you must have quite the hunk of gold!
Slide 9 = A. longer
If you walk to the east, you are pushing the earth towards the west which is the opposite of how it spins so you would slow down the spin and lengthen the day
Slide 10 = 800N
The tree pulls back as hard as the guy pulls forward
Slide 11 = 800 N
If nothing was on 1 side of the rope, it would be slack and the scale would read 0 N. Since you can’t pull harder on one side of a rope than on the other side, each pulls w 800 N. Guy #2 is just like the tree in the pervious question
Slide 12 = 800 N
You are only as strong as your weakest link. The guy is going to go flying towards Chuck Norris but the guy can only pull back with 800 N so the max tension in the rope is 800 N so that’s what the scale reads.
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19. Slide 14 = a = Fa/mtotal = 2500N / 7100.2kg = 0.35 m/s2
Slide 13= C
b/c 3rd law
Slide 14 = a = Fa/mtotal = 2500N / kg = 0.35 m/s2
Follow up: If you had to stand between 2 of the cages, which ones and why? Get less squished b/t mouse and chimp b/c all you would have to push would be the mouse. In other words, must of the F gets used up pushing the other 2 cages and not much would be left to push on you.
This is called the contact force.
What is the contact force between the chimp’s cage and the mouse’s cage?
Fc,m = mma = 0.2 kg * 0.35 m/s2 = 0.07 N
What is the contact force between the chimp’s cage and the elephant’s cage?
Fc,e = mm+Ca = kg * 0.35 m/s2 = N
Slide 15 = FT1 = mma = 0.2 kg * 0.35 m/s2 = 0.07 N
FT2 = mm+ca = (100 kg kg) * 0.35 m/s2 = N
Slide 17 = B; not A because they don’t depend on each other
Slide 18 = B b/c pink arrow shows box 3 acting on box 4 (F3,4) so the reaction to that is F4,3
Slide 19 = C & D
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