III - 1 II. Newton's Laws of Motion Concept Review Warm-Up ...

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CAN YOU EXPLAIN THIS 1. Hand Slam Why does it hurt more if you slam the back of your hand against the wall when you are holding a book compared to when your hand is empty Which of Newton’s laws is most useful for explaining this observation 2. Coin Flick Try this yourself. Set a 3x5 index card on top of a glass and place a coin on top of the card over the center of the glass. Flick the edge of the card quickly with your index finger and the coin falls into the glass. Can you explain the motions of both the coin and the card using Newton’s laws of motion 3. The Myth of ‘Hang-Time’ Use Newton’s laws to explain why it is impossible for a basketball player to have a ‘hang time’ when jumping into the air to make a shot. 4. String Pull You can try this yourself if you can find an object with a mass around 1 kilogram that has two hooks or holes on opposite sides, so that you can tie two strings to it. If you do try this, it is important that the string is made of cotton: you will never be able to break a nylon string! Tie a string to each side of the heavy object. Hold the object in the air with one string. III - 10
Pull the lower string quickly and the lower string breaks. Pull the lower string slowly and the upper string breaks. Warning: If you try this yourself, make sure the mass is not too heavy and move your hand out of the way so it doesn’t get hit by the falling mass! Can you explain these results using Newton’s laws of motion Which of Newton’s law(s) are most useful for explaining the observations made in each situation 5. Air Bags and Seat Belts Use Newton’s laws of motion to explain how an air bag is able to save a person’s life in a headon car crash. Why is an air bag dangerous to a small person, young child, or infant Use Newton’s laws of motion to explain how seat belts are able to save a person’s life in a car crash. Why are seat belts a useful safety device no matter what the direction of impact, but air bags are most effective in head-on collisions 6. Tug of War The physics class is having an imaginary tug of war — the men against the women. For a long time the two teams are pulling with equal force and the knot in the center of the rope isn’t going anywhere. But then Frank sneezes and stops pulling as hard for just a few seconds. Of course, he quickly recovers, and the two sides are pulling with equal strength once again. “Is it possible”, Mr. Nicholls asks, “to determine who wins the tug of war based on this information” “Of course not,” Frank says, “The other team was pulling with greater force for a short time, but the two forces are equal again. So the knot in the middle moved a little bit towards the girls’ side but then stopped. The tug of war isn’t over yet.” “Wait a minute,” Cathy says, “You have to listen carefully to the set-up. Mr Nicholls said that the girls were pulling harder for a short time, but then the boys recovered and began pulling with the same force as they were before. That means that our side won! Right Mr. Nicholls” Cathy is right: the women do win the tug of war. But can you apply Newton’s laws correctly to explain why that is the case III - 11
Page 1 and 2: II. Newton’s Laws of Motion Conce
Page 3 and 4: 2. A 3 kg mass is accelerated by a
Page 5 and 6: Which prediction do you believe is
Page 7 and 8: QUALITATIVE REASONING General Hint:
Page 9: Would the spring scale read 0, 10,

III - 1 II. Newton's Laws of Motion Concept Review Warm-Up ...

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