7. Friction, Inclines, Systems

A block $1$ rests on a horizontal surface and is connected by a light string over a frictionless pulley to a hanging block $2$. If block $2$ is heavier and tends to pull block $1$ to the right, in which direction does the static friction force act on block $1$?

Which of the following best describes the difference between $f\_\mathrm{static}$ (static friction) and $f\_\mathrm{kinetic}$ (kinetic friction)?

When you walk across a carpet and then touch a metal object, you often feel a shock. Which of the following best explains this phenomenon in terms of static friction?

Which type of friction is generally more difficult to overcome when starting to move an object at rest on a surface?

A block of mass $m$ rests on an inclined plane that makes an angle $\theta$ with the horizontal. What is the minimum coefficient of static friction required to prevent the block from sliding down the plane?

Which type of friction acts on an object that is not moving?

A box of bananas weighing $40.0$ N rests on a horizontal surface. The coefficient of static friction between the box and the surface is $0.40$, and the coefficient of kinetic friction is $0.20$. What minimum horizontal force must the monkey apply to start the box in motion?

Which of the following is an example of a static friction process?

A crate rests on a horizontal floor. If the coefficient of static friction between the crate and the floor is $\mu s_{}$ = $0.5$, what is the maximum possible static friction force that can act on a $20$ kg crate before it starts to move? (Assume $g$ = $9.8$ ms-2.)

The 70.0-kg climber in Fig. 5–53 is supported in the 'chimney' by the friction forces exerted on his shoes and back. The static coefficients of friction between his shoes and the wall, and between his back and the wall, are 0.80 and 0.60, respectively. What is the minimum normal force he must exert? Assume the walls are vertical and that the static friction forces are both at their maximum. Ignore his grip on the rope.

A cyclist is riding on a flat road and needs to make a turn of radius $r$ at a constant speed $v$ without skidding. What is the minimum possible coefficient of static friction between the bike tires and the ground required to safely make the turn?

A pickup truck is carrying a toolbox, but the rear gate of the truck is missing. The toolbox will slide out if it is set moving. The coefficients of kinetic friction and static friction between the box and the level bed of the truck are $0.355$ and $0.650$, respectively. Starting from rest, what is the shortest time this truck could accelerate uniformly to $30.0$ m/s without causing the box to slide? Draw a free-body diagram of the toolbox.