Chapter 8
Lightweight because they have less rotational inertia than heavy wheels
Should you enter a soapbox derby contest using heavier or lightweight wheels?
No, zero lever arm means zero torque
When the line of action of force intersects the center of mass of an object, can that force produce a torque about the object's center of mass?
The softball because it has a smaller rotational inertia compared to its mass
A softball and a basketball start from rest and roll down an incline. Which ball reaches the bottom first?
As more skyscrapers are built, the radial distance from the earth's center axis increases, causing the earth to rotate slower. This makes the days a bit longer
As more and more skyscrapers are built on the surface of earth, does the day tend to become larger or shorter?
No, torque requires a force and a lever arm
Can a force produce a torque when there is no lever arm?
No, in the absence of force an object moves straight
Can an object move along a curved path if no force acts on it?
Sue's because they have to turn more times to cover the same distance
Dan and Sue cycle at the same speed. The tires on Dan's bike are larger in diameter than those on Sue's bike. Which wheels have the greater rotational speed?
The ocean surface would be higher, therefore further away from the center of rotation of the earth, increasing the radial distance of mass. This would cause the rotation speed to decrease
If the polar ice caps on earth's solid surface were to melt, the oceans would be deeper. What effect would this have on earth's rotation?
You tend to move in a straight line, but since the car is turning, the door is in the way of that straight line, so you lean into it. The push by the door against you provides a centripetal force which keeps you along the curved path, and from being thrown out of the car
When you are in the front passenger seat of a car turning to the left, you may find yourself pressed against the right-side door. Why do you press against the door?
Friction on the road by the tires creates a torque about the car's center of mass. Accelerating causes the friction force to point forward, making the car nose up, and decelerating causes the opposite
Why does a car nose up when accelerating and nose down when braking?
When rocking, a bus partially rotates about its center of mass, therefore being farther away from the center means more rocking, like a seesaw
Why does sitting closer to the center of a vehicle provide the most comfortable ride in a bus traveling on a bumpy road, in a ship in a choppy sea, of in an airplane in turbulent air?
The rotational inertia of the turntable increases as you crawl outward, decreasing the angular speed
You sit at the middle of a large turntable at an amusement park as it is set spinning and then allowed to spin freely. When you crawl toward the edge of the turntable, does the rate of rotation increase, decrease, or stay the same?
