Frictional and Normal Forces

What is the frictional force on a 25-N object sliding along a horizontal surface at constant speed if the coefficient of kinetic friction is 0.40?

• 10 N

• 25 N

• 4.0 N

• 8.0 N

A 50.0-N box rests on an inclined plane whose angle of inclination is 30.0 degrees. What is the normal force acting on the object?

• 25 N

• 32 N

• 43 N

• 50 N

A 25-N box lies on top of a 50-N box. What is the normal force acting on the 50-N box?

• There is none.

• 25 N

• 50 N

• 75 N

A 65-N box rests on an a 40.0-degree inclined plane. What is the coefficient of static friction if the box were to experience pending motion at this angle?

• 0.50

• 0.64

• 0.72

• 0.83

A 60-N box moves on a 65-degree inclined plane. If the coefficient of kinetic friction is 0.25, by how much is the box accelerated?

• 7.8 m/s/s

• 9.8 m/s/s

• 3.2 m/s/s

• 1.9 m/s/s

Which of the following statement about friction is not true?

• Friction is always parallel to the contact surface.

• Friction is always opposite the direction of motion.

• Frictional force is inversely proportional to the normal force of the object.

• Friction does not depend on the area of contact between the object and the surface

Which is the unit for the coefficient of friction?

• newton

• N/m²

• N-m

• It is dimensionless.

What is the normal force exerted by the ground on a 65-kg metal bar?

• 65 N

• 640 N

• -65 N

• -640 N

Tags

NGSS.HS-PS2-1

Which explains why there is less force needed once a heavy object starts moving from an initial state of rest?

• The inertia of the object is now less than when it is at rest.

• The force exerted is now greater than the normal force.

• The parallel force is now greater than the weight of the object.

• The coefficient of kinetic friction is less than the coefficient of static friction.

The normal force on an object is a consequence of which law?

• First Law of Motion

• Second Law of Motion

• Third Law of Motion

• Law of Universal Gravitation

Tags

NGSS.HS-PS2-1