Frictional Forces

Multiple Choice

Which of the following is a likely effect when there is a lot of friction during a soccer game?

• The ball moves faster across the field

• Players find it easier to stop quickly

• The ball slides smoothly without stopping

• Players have difficulty changing direction

Open Ended

How does frictional force play a role in everyday activities such as sports?

Multiple Choice

What happens to a person's movement when there is barely any friction, as shown in the image?

• They move smoothly and quickly without resistance.

• They remain stationary and cannot move.

• They move slowly due to high resistance.

• They fall down immediately.

Open Ended

Explain how the microscopic model of friction helps us understand why rough surfaces create more resistance.

Fill in the Blanks

Static friction is opposite the push to prevent

.

Open Ended

Describe the difference between the direction of kinetic friction and the direction of motion of an object.

Multiple Select

Which of the following statements are true about static and kinetic friction?

• Static friction acts when an object is at rest.

• Kinetic friction acts when an object is moving.

• Static friction is always greater than kinetic friction.

• Kinetic friction prevents objects from starting to move.

Fill in the Blanks

The equation for frictional force is

= μF_N.

Open Ended

Describe a real-life scenario where reducing the coefficient of friction is beneficial, and explain why.

Multiple Select

Select all surfaces from the table that have a coefficient of kinetic friction less than 0.05.

• Ice on ice

• Metal on metal (lubricated)

• Teflon on Teflon in air

• Joints in human limbs

Multiple Choice

Which surface combination has the highest coefficient of static friction according to the table?

• Wood on wood

• Rubber on dry concrete

• Steel on steel (unlubricated)

• Ice on ice

Fill in the Blanks

If the coefficient of static friction is 0.82 between the floor and a 900 N desk, what force must be used to move the desk from rest?

Open Ended

Explain how the coefficient of friction affects the force required to move an object from rest, using the desk example and the table of coefficients.

Multiple Choice

What is the force of friction acting on a 7.6 kg object pulled along a horizontal surface with a coefficient of friction of 0.20?

• 14.9 N

• 7.6 N

• 74.48 N

• 1.52 N

Fill in the Blanks

A sled has mass 15 kg. A horizontal pull of 25.01 N will just move the sled when it is on a horizontal surface of compacted snow. What is the coefficient of friction?

Fill in the Blanks

A 10 kg object is pulled along a horizontal surface by an applied force of 50 N. If its acceleration is 2 m/s2, what is the coefficient of friction between the two surfaces?

Multiple Select

Select all the variables that are needed to calculate the force of friction acting on an object on a horizontal surface.

• Normal force

• Coefficient of friction

• Mass of the object

• Applied force

Multiple Choice

Which of the following values is closest to the coefficient of friction for a sled of mass 15 kg that requires a horizontal pull of 25.01 N to just start moving on compacted snow?

• 0.17

• 0.31

• 0.20

• 0.82

Open Ended

Explain how the coefficient of friction can be determined if the applied force, mass, and acceleration of an object are known.

Fill in the Blanks

Frictional force is important in sports like soccer because it helps players to

quickly.

Open Ended

How does friction affect the movement of a soccer ball on different surfaces?