A 15 kg box sits on a table. The coefficient of static friction $\mu_s$ between table and box is 0.3, and the coefficient of kinetic friction $\mu_k$ is 0.2.

(a) What is the force required to start the box moving?

A $12 \mathrm{~kg}$ computer is sitting on a table and the coefficient of static friction between the computer and the table is $0.7$. If the computer is pushed with a horizontal $30 \mathrm{~N}$ force, what is the actual force of static friction between the computer and the table?

Zorch, an archenemy of Superman, decides to slow Earth's rotation to once per 28.0 h by exerting an opposing force at and parallel to the equator. Superman is not immediately concerned, because he knows Zorch can only exert a force of $4.00\times10^7$ N (a little greater than a Saturn V rocket's thrust). How long must Zorch push with this force to accomplish his goal? (This period gives Superman time to devote to other villains.) Explicitly show how you follow the steps found in Problem-Solving Strategy for Rotational Dynamics.

Find the derivative of each function at the number indicated using a graphing utility. $f(x)=x \sec x$ at $\frac{\pi}{6}$

A box with a mass of $2.2 \mathrm{~kg}$ sits on top of another box with a mass of $3.8 \mathrm{~kg}$. The coefficient of friction between the two boxes is $0.25$, and the coefficient of kinetic friction between the larger box and the horizontal surface is $0.32$. Determine the largest horizontal force that can be applied to the larger box so that the smaller box does not slip off.

A box of mass 12.0 kg sits at rest on a horizontal surface. The coefficient of kinetic friction between the surface and the box is 0.300. The box is initially at rest, and then a constant force of magnitude F and direction 37.0$^{\circ}$ below the horizontal is applied to the box; the box slides along the surface.

What is F if the surface is frictionless and all the other quantities are the same?

A ball whose mass is 1.4 kg is suspended from a spring whose stiffness is 4 N/m. The ball oscillates up and down with an amplitude of 14 cm. (a) What is the angular frequency !?

A 5.0-kg box rests on a horizontal surface. The coefficient of kinetic friction between the box and surface is

$$μ_K = 0.50.$$

A horizontal force pulls the box at constant velocity for 10 cm. Find the work done by (a) the applied horizontal force, (b) the frictional force, and (c) the net force.

(b) With the two boxes starting from rest, explain qualitatively what Alice and Bob did to get their boxes moving at different constant speeds.

A box of mass of 100 kg sits on a horizontal surface. A rope that makes an angle of 40° with the horizontal surface is connected to the box, and it is pulled with a force of 280 N. If the box is moved at a constant velocity along the surface, what is the coefficient of friction for the surface?

A 5 kg box with initial speed 4 m/s slides across the floor and comes to a stop after 0.7 s. (a) What is the coefficient of kinetic friction?

What is the Spanish word for dishwasher?

When you apply a force of 100 N, what is the magnitude of the horizontal component of the force that the floor exerts on the block?

You put a 3 kg block in the box, so the total mass is now 8 kg, and you launch this heavier box with an initial speed of 4 m/s. How long does it take to stop?