How Things Work: An Introduction to Physics week 6

In this blog you will find the correct answer of the Coursera quiz How Things Work: An Introduction to Physics week 6 mixsaver always try to brings best blogs and best coupon codes
 

 

Week- 6

Wheels

 

1. You are walking at constant velocity on a sidewalk that slopes gently uphill. What force(s) is the sidewalk exerting on you?

 

2. For millennia, people have ground grain into flour by placing a thin layer of grain between two surfaces that slide across one another. Those two surfaces are usually stacked on top of one another and the surface above the grain is that of a very heavy object, such as a millstone. When motionless, the heavy millstone will exert large support forces on the grain and thereby crush that grain to some extent, but it won’t make fine flour. Spinning the millstone while keeping the surface below the grain motionless, however, will grind the grain as fine as you like. What role does the millstone’s weight play in this grinding process?

 

3. Walking on ice can be treacherous, but some techniques are safer than others. In general, you are less likely to slip and fall if you lower your foot vertically into place on the ice as you take each step than you are if you slide your foot horizontally into place on the ice as you take each step. Why is the vertical landing method of walking on ice usually safer than the horizontal sliding method?

 

4. Most automobiles have mechanical brakes on all four of their wheels. Each of these brakes consists of two surfaces—one surface that rotates with the wheel and one surface that doesn’t rotate. When you put your foot on the brake pedal in such an automobile, those two surfaces begin to slide across one another. The harder you press on the brake pedal, the more tightly those surfaces are pressed against one another. Why do the brakes permit the two surfaces to slide across one another, rather than locking those two surfaces together so that they don’t slide across one another?

 

5. The harder you press on an automobile’s brake pedal, the greater the support forces that the two surfaces in each brake exert on one another. Why does this increase in support forces in the brakes result in more rapid deceleration (acceleration opposite its velocity) of the automobile?

 

6. The front wheel of your bicycle spins freely on its axle and rotates at almost constant angular velocity if nothing outside the bicycle exerts a torque on it. Suppose the front wheel is motionless as you stand next to your bicycle. You get on the bicycle and pedal forward. As the bicycle begins to move forward, why does its front wheel begin to rotate?

 

7. When you drive a car on a level (horizontal) road that is slippery with ice, you usually have no problems except when you try to speed up, slow down, or turn. Why does the icy road make those three actions hazardous? [neglect any effects due to air]

 

8. Pedaling your bicycle provides power to its rear wheel and propels your bicycle forward. What force(s) is principally responsible for the bicycle’s forward acceleration as you pedal your bicycle forward from rest on a level (horizontal) road?

 

9. If you throw a ball directly upward at 10 meters-per-second (22 mph), it will rise upward about 5 meters before coming momentarily to a stop. If you throw that ball directly upward at 20 meters-per-second (44 mph), how far will it rise upward before coming momentarily to a stop?

 

10. Earth’s oceans exhibit tides, so that the average water level near most shores rises and falls at roughly six-hour intervals. A somewhat simplistic explanation for the tides is that the moon’s and sun’s gravity slightly distort Earth’s oceans, creating high and low regions, and the Earth’s rotation causes those high and low regions to shift on the Earth’s surface. There are a few tidal generating plants on Earth that use energy in the tides to generate electricity. Where does nearly all of the energy in the tides originally come from?

 

 

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