# Physics

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1.
1 point
While you’re weighing yourself on a bathroom scale, you reach out and push downward on a nearby table. Is the weight reported by the scale high, low, or correct?
2.
1 point
A hammer’s weight is downward, so how can a hammer push a nail upward into the ceiling?
3.
1 point
To weigh an infant you can step on a scale once with the infant and then again without the infant. Why is the difference between the scale’s two readings equal to the weight of the infant?
4.
1 point
A salad spinner is a rotating basket that dries salad after washing. How does the spinner extract the water?
5.
1 point
As you swing back and forth on a playground swing, your apparent weight changes. At what point do you feel the heaviest?
6.
1 point
As your car reaches the top in a smoothly turning Ferris wheel, which way are you accelerating?
7.
1 point
The crank of a hand-operated kitchen mixer connects to a large gear. This gear meshes with smaller gears attached to the mixing blades. Since each turn of the crank makes the blades spin several times, how is the force you exert on the crank handle related to the forces the mixing blades exert on the batter around them?
8.
1 point
Most racing cars are built very low to the ground. While this design reduces air resistance, it also gives the cars better dynamic stability on turns. Why are these low cars more stable than taller cars with similar wheel spacings?
9.
1 point
You board an elevator with a large briefcase in your hand. Why does that briefcase suddenly feel particularly heavy when the elevator begins to move upward?
10.
1 point
Why must the surface of a hammer be very hard and stiff for it to drive a nail into wood?
11.
1 point
Padded soles in running shoes soften the blow of hitting the pavement. Why does padding reduce the forces involved in bringing your foot to rest?
12.
1 point
When you turn while riding a bike, you must lean in the direction of a turn or risk falling over. If you lean left as you turn left, why don’t you fall over to the left?
13.
1 point
Why does it hurt less to land on a soft foam pad than on bare concrete after completing a high jump?
14.
1 point
If the bottom of your bicycle’s front wheel becomes caught in a storm drain, your bicycle may flip over so that you travel forward over the front wheel. Explain this effect in terms of rotation, torque, and center of mass.
15.
1 point
When a moving hammer hits a nail, it exerts the enormous force needed to push the nail into wood. This force is far greater than the hammer’s weight. How is it produced?
16.
1 point
Sprinters start their races from a crouched position with their bodies well forward of their feet. This position allows them to accelerate quickly without tipping over backward. Explain this effect in terms of torque and center of mass.
17.
1 point
Astronauts learn to tolerate weightlessness by riding in an airplane (nicknamed the “vomit comet”) that follows an unusual trajectory. How does the pilot direct the plane in order to make its occupants feel weightless?
18.
1 point
The starter motor in your car is attached to a small gear. This gear meshes with a large gear that’s attached to the engine’s crankshaft. The starter motor must turn many times to make the crankshaft turn just once. How does this gearing allow modest forces inside the starter motor to turn the entire crankshaft?
19.
1 point
If you put your bathroom scale on a ramp and stand on it, will the weight it reports be high, low, or correct?
20.
1 point
When you step on a scale, it reads your weight plus the weight of your clothes. Only your shoes are touching the scale, so how does the weight of the rest of your clothes contribute to the weight reported by the scale?
21.
1 point
People falling from a high diving board feel weightless. Has gravity stopped exerting a force on them? If not, why don’t they feel it?
22.
1 point
If you drop a steel marble on a wooden floor, why does the floor receive most of the collision energy and contribute most of the rebound energy?
23.
1 point
When you lie on a spring mattress, it pushes most strongly on the parts of you that stick into it the farthest. Why doesn’t it push up evenly on your entire body?
24.
1 point
Curly hair behaves like a weak spring that can stretch under its own weight. Why is a hanging curl straighter at the top than at the bottom?