If there is a net force on a particle in uniform circular motion, why doesn’t the particle’s speed change?

Solve each inequality.

$$w-8<3$$

It is often said that “friction always opposes motion.” Give at least one example in which (a) static friction causes motion, and (b) kinetic friction causes motion.

_____ in cellular respiration, a cycle of chemical reactions that break down glucose and produce ATP; energizes electron carriers that pass the energized electrons on to the electron transport chain.

On your electrical "power" bill, you are charged for kilowatthours ( $\mathrm{kWh}$ ). Is this really a power bill? What kind of quantity is the kilowatt-hour?

A 5.00-kg box sits at rest at the bottom of a ramp that is 8.00 m long and is inclined at $30.0^{\circ}$ above the horizontal. The coefficient of kinetic friction is $\mu \mathrm{k}=0.40$, and the coefficient of static friction is $\mu s=0.43$. What constant force F, applied parallel to the surface of the ramp, is required to push the box to the top of the ramp in a time of 6.00 s?

A block rests on an inclined plane with enough friction to prevent it from sliding down. To start the block moving, is it easier to push it up the plane or down the plane? Why?

In a world without friction, which of the following activities could you do (or not do)? Explain your reasoning. (a) drive around an unbaked highway curve; (b) jump into the air; (c) start walking on a horizontal sidewalk; (d) climb a vertical ladder; (c) change lanes on the freeway.

A woman in an elevator lets go of her briefcase, but it does not fall to the floor. How is the elevator moving?

You are pushing a large crate from the back of a freight elevator to the front as the elevator is moving to the next floor. In which situation is the force you must apply to move the crate the least, and in which is it the greatest: when the elevator is accelerating upward, when it is accelerating downward, or when it is traveling at constant speed? Explain.

On an icy road, you approach a curve that has the banking angle calculated for $55 \mathrm{mph}$. Your passenger suggests you slow down below $55 \mathrm{mph}$, just to be on the safe side, but you say that you should maintain your speed at $55 \mathrm{mph}$.
(a) Who is correct, you or your passenger?
(b) What would happen if you were to slow down (or speed up)?
(c) Would your passenger's suggestion be a good one on an unbanked road?

A clothesline hangs between two poles. No matter how tightly the line is stretched, it sags a little at the center. Explain why.

In uniform circular motion, what are the average velocity and average acceleration for one revolution? Explain.

When you stand with bare feet in a wet bathtub, the grip feels fairly secure, and yet a catastrophic slip is quite possible. Explain this in terms of the two coefficients of friction.