Friction Questions and Answers

Place the notebook on a table, and push it a few inches with your finger. When it moves, it has kinetic energy. Which kind of force opposed the motion of the notebook?

8. Two packages are connected by a very light string that goes over an ideal pulley as shown in the figure. Package A has a mass of 3.0 kg and can slide along a rough plane inclined at 30° above the horizontal. The string acts on package A parallel to the surface of the plane. The coefficient of static friction between package A and the plane is 0.40. What minimum mass should package B have in order to start package A sliding up the ramp

14. The figure shows two crates, each of mass m = 24 kg, that are connected by a very light wire. The coefficient of kinetic friction between the crate on the inclined surface and the surface itself is 0.31. Find the speed of the crates after they have moved 1.6 m starting from rest.

A 9.3 kg stone on a flat floor is pushed with a force of 18.9 N to the right. If the coefficient of static and kinetic friction between the stone and the floor are μ, = 0.60,μ = 0.14, what is the frictional force on the stone?

41. (II) A 2.0-kg silverware drawer does not slide readily. The owner gradually pulls with more and more force, and when the applied force reaches 9.0 N, the drawer suddenly opens, throwing all the utensils to the floor. What is the coefficient of static friction between the drawer and the cabinet?

Wings on race cars push them into the track. The increased normal force makes large friction forces possible. At one Formula One racetrack, cars turn around a half-circle with diameter 190 m at 68 m/s. For a 610 kg vehicle, the approximate minimum static friction force to complete this turn is A. 15000 N B. 6000 N C. 24000 N D. 18000 N E. 30000 N

A 6.0-kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If the coefficient of kinetic friction is 0.40, at what rate does the box accelerate down the slope? A. 3.4 m/s² B. 4.1 m/s² C. 3.7 m/s² D. 3.1 m/s²

You push horizontally on a 120-N box that is initially resting on a horizontal table. The coefficient of static friction between the box and the table is 0.75, and the coefficient of kinetic friction is 0.40. Find the friction force on the box if the push is equal to (a) 84 N; (b) 94 N.

A 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the surface is 0.40, a the coefficient of kinetic friction is 0.30. What is the force of friction on the box? A. 220 N B. 32 N C. 250 N D. 620 N E. 200 N

A 200-g hockey puck is launched up a ramp that is inclined at a 30° angle above the horizontal. The coefficients of static and kinetic friction between the puck and the ramp are µs = 0.40 and µk = 0.30, respectively, and the puck's initial velocity at the base is 3.8 m/s parallel to the sloping surface of the ramp. What speed does the puck have when it slides back down to its starting point?

Match the following formulas about calculating friction: Always works. FN can be found by summing all the y-dir forces, recognizing that the acceleration in the y-dir is (probably) zero, and solve for FN Works whenever the surface is horizontal and there are no y-direction forces except for gravity and the normal force Works whenever the surface is an inclined plane and there are no y-direction forces except for gravity and the normal force 1. Ff = μmg 2. Ff= μmg cos θ 3. F₁ = μ FN

A stone initially moving at 8.0 m/s on a level surface comes to rest due to friction after it travels 11 m. What is the coefficient of kinetic friction between the stone and the surface? A. 0.80 B. 0.13 C. 10.25 D. 0.43 E. 0.30

A coin is placed 13.0 cm from the axis of a rotating turntable of variable speed. When the speed of the turntable is slowly increased, the coin remains fixed on the turntable until a rate of 38.0 rpm (revolutions per minute) is reached, at which point the coin slides off. What is the coefficient of static friction between the coin and the turntable?

Consider the system shown in the figure. Block A (5 kg) and block B (2 kg). Once block B is set into downward motion, it descends at a constant speed. Calculate the coefficient of kinetic friction between block A and the tabletop. 1.0 0.2 0.4 0.8 -0.5

A 226 Hz tone is played in a chamber filled with room temperature helium at atmospheric pressure. The speed of sound in helium under these conditions is 979 m/s. What will be the wavelength of the sound wave produced from this tone? Select one: a. 1170 m b. 11.7 m c. 4.33 m d. 7.23 m

(a) If the crate doesn't move, what's the magnitude of the static friction force (in N)? N (b) What is the minimum possible value of the coefficient of static friction between the crate and the floor? (Assume the crate remains stationary.)

A 1,587-kg car starts from rest at the top of a driveway 6.58 m long that is sloped at an angle of 26 degrees with the horizontal. If an average friction force of 2,003 N impedes the motion of the car, find the speed (in m/s) of the car at the bottom of the driveway. Use the approximation that g = 10 m/s². Answer: m/s (round tothe nearest hundredth)

Three cars (car F, car G, and car H) are moving with the same velocity when the driver suddenly slams on the brakes, locking the wheels. The most massive car is car F, the least massive is car H, and all three cars have identical tires. Which car travels the longest distance to skid to a stop? A. Car F B. Car G C. Car H They all travel the same distance in stopping. can't be determined from the given information.

Study the diagram. A fridge has height h, width w, and mass m, which we assume is distributed uniformly throughout the volume of the fridge. A person pushes on the fridge with a horizontal force of magnitude F, applied at a height H above the floor. The coefficient of static friction between the floor and the feet of the fridge is us. Answer the following questions: (A) Assuming sufficiently large μs, what is Fe, the critical value of F that brings the fridge to the verge of tipping, i.e., on the verge of the left feet losing contact with the floor? DRAW A BOX AROUND YOUR FINAL ANSWER. (B) Suppose μs = 1. What is the maximum height-to-width ratio of the fridge so that the fridge will slide before it tips, even if the person pushes at the top of the fridge? DRAW A BOX AROUND YOUR FINAL ANSWER. In your box, sketch the shape of the fridge in this case.

Initially at rest, a box moves down an incline which is 25 degrees up from the horizontal. While the box is moving down the incline, the friction between the box and the surface is 0.200. After sliding a distance of 10.4 m down the incline, the box continues off the edge without slowing down. The box lands on a surface which is 3.5 m below the edge of the incline. What speed does the box have just before it lands?

At an accident scene on a level road, investigators measure a car's skid mark to be 109 m long. It was a rainy day and the coefficient of friction was estimated to be 0.49. Use these data to determine the speed of the car when the driver slammed on (and locked) the brakes.

IP A 37-kg crate is placed on an inclined ramp. When the angle the ramp makes with the horizontal is increased to 24 °, the crate begins to slide downward. What is the coefficient of static friction between the crate and the ramp? Express your answer using two significant figures.

It would be expected that as the angle of an incline increases, the coefficient of static friction must also increase in order to maintain rolling without slipping. Is this supported by the math of this unit? Explain.