Friction (static and kinetic) Knowledge-Based Download PDF

Questions

1. 1.

   A 4 kg block rests on an adjustable inclined plane. When the angle of inclination is gradually increased to $37^\circ$, the block is on the verge of sliding down the plane. What is the coefficient of static friction between the block and the plane? (Take $g = 10\text{ m/s}^2$, $\sin 37^\circ = 0.60$, and $\cos 37^\circ = 0.80$.)

   • A) 0.48
   • B) 0.60
   • C) 1.33
   • D) 0.75
2. 2.

   A 10 kg box rests on the floor of an elevator that is accelerating upward at $2.0\text{ m/s}^2$. If the coefficient of static friction between the box and the floor is 0.40, what is the maximum horizontal force that can be applied to the box without causing it to slide? (Take $g = 10\text{ m/s}^2$.)

   • A) 32 N
   • B) 40 N
   • C) 48 N
   • D) 60 N
3. 3.

   A 6 kg block on a rough horizontal tabletop is connected by a light string over a frictionless pulley to a hanging mass $m$. If the coefficient of static friction between the block and the tabletop is 0.45, what is the maximum value of $m$ that allows the system to remain in equilibrium? (Take $g = 10\text{ m/s}^2$.)

   • A) 1.35 kg
   • B) 1.80 kg
   • C) 2.25 kg
   • D) 2.70 kg
4. 4.

   A 2 kg block rests on top of a 3 kg block, which sits on a frictionless horizontal floor. If the coefficient of static friction between the two blocks is 0.40, what is the maximum horizontal force that can be applied to the 3 kg block so that both blocks accelerate together without slipping? (Take g = 10 m/s².)

   • A) 8 N
   • B) 12 N
   • C) 15 N
   • D) 20 N
5. 5.

   A box is projected across a rough horizontal floor with an initial speed of 12 m/s. If the coefficient of kinetic friction between the box and the floor is 0.30, how far does the box slide before coming to rest? (Take $g = 10\text{ m/s}^2$.)

   • A) 18 m
   • B) 24 m
   • C) 36 m
   • D) 48 m
6. 6.

   A 6 kg crate slides down a ramp inclined at $37^\circ$ to the horizontal. If the coefficient of kinetic friction between the crate and the ramp is 0.25, what is the magnitude of the crate's acceleration down the ramp? (Take $g = 10\text{ m/s}^2$, $\sin 37^\circ = 0.60$, and $\cos 37^\circ = 0.80$.)

   • A) 2.0 m/s²
   • B) 4.0 m/s²
   • C) 6.0 m/s²
   • D) 8.0 m/s²
7. 7.

   A 10 kg block is pulled along a flat horizontal surface by a force of 50 N directed at an angle of $37^\circ$ above the horizontal. If the coefficient of kinetic friction between the block and the surface is 0.20, what is the magnitude of the kinetic friction force exerted on the block? (Take $g = 10\text{ m/s}^2$, $\sin 37^\circ = 0.60$, and $\cos 37^\circ = 0.80$.)

   • A) 8 N
   • B) 12 N
   • C) 14 N
   • D) 20 N
8. 8.

   A student presses a 2 kg book against a vertical wall by applying a horizontal force $F$. If the coefficient of static friction between the book and the wall is 0.40, what is the minimum magnitude of $F$ required to prevent the book from sliding down? (Take g = 10 m/s².)

   • A) 8 N
   • B) 20 N
   • C) 50 N
   • D) 80 N
9. 9.

   A 5 kg crate is pushed along a horizontal surface by a constant horizontal force of 26 N. If the coefficient of kinetic friction between the crate and the surface is 0.40, what is the magnitude of the crate's acceleration? (Take $g = 10\text{ m/s}^2$.)

   • A) $0.6\text{ m/s}^2$
   • B) $1.0\text{ m/s}^2$
   • C) $1.2\text{ m/s}^2$
   • D) $4.0\text{ m/s}^2$
10. 10.

    A 4 kg block rests on a rough horizontal floor where the coefficient of static friction is 0.5 and the coefficient of kinetic friction is 0.3. If a horizontal pulling force of 15 N is applied to the block, what is the magnitude of the friction force exerted by the floor on the block? (Take $g = 10\text{ m/s}^2$.)

    • A) 20 N
    • B) 15 N
    • C) 12 N
    • D) 3 N