Friction, Drag, and Elasticity

It is a force that opposes relative motion between surfaces in contact.

• Friction

• Tension

• Normal Force

• Gravity

• Applied Force

Friction acts ____________ to the surface between surfaces and always _____________ the direction of motion

• parallel; opposite to

• perpendicular; opposite to

• parallel; the same to

• perpendicular; the same to

• cross; perpendicular to

If two surfaces are in contact and moving relative to one another, then the friction between them is __________________

• kinetic friction

• static friction

• potential friction

• rolling friction

Kinetic friction is usually greater than the static friction between the surfaces.

• False

• True

Friction is proportional to the normal force but not to the area in contact.

• False

• True

Which of the following shows the relationship of drag force (F_D) and speed of the object?

• F_D is proportional to v²

• F_D is inversely proportional to v²

• F_D is proportional to v

• F_D is inversely proportional to v

• F_D is equal to v²

Which of the following receives the lowest drag force, provided that other variables are the same?

• Toyota Camry (C = 0.28)

• Honda Civic (C = 0.36)

• Ferrari (C = 0.37)

• Hummer H2 SUV (C = 0.64)

In which surface system would an object easier to move?

• Wood on wood (μs = 0.55, μk = 0.35)

• Metal on wood (μs = 0.50, μk = 0.30)

• Steel on steel (μs = 0.6, μk = 0.3)

• Rubber on dry concrete (μs = 1.0, μk = 0.7)

• Steel on Ice (μs = 0.04, μk = 0.02)

A skydiver falling through air reaches a constant velocity which is called as ____________________.

• terminal velocity

• terminal force

• tangent velocity

• drag velocity

• average velocity

The terminal velocity of an object was achieved when

• drag force balances the gravity.

• drag force is larger than gravity.

• drag force is less than the gravity.

• when drag force is zero.

• gravity is zero.