Unit 4 Summary

Front

What is static friction?

Back

Static friction is the force that keeps an object at rest and prevents it from moving when a force is applied. It must be overcome for the object to start moving.

Front

What is kinetic friction?

Back

Kinetic friction is the force that opposes the motion of an object that is already in motion. It is usually less than static friction.

Front

What happens to the speed of a block being pulled with a force equal to its kinetic friction?

Back

The block will continue at a constant speed in the direction that it is being pulled.

Front

What is terminal velocity?

Back

Terminal velocity is the constant speed that a freely falling object eventually reaches when the resistance of the medium (like air) prevents further acceleration.

Front

When an object reaches terminal velocity, what is true about the forces acting on it?

Back

The force of air resistance equals the object's weight.

Front

How does mass affect the force of air resistance on an object?

Back

Objects with more mass (and inertia) are less affected by the force of air resistance.

Front

What is the relationship between force and pulley systems?

Back

In an ideal pulley system with no friction, the force needed to lift a load is equal to the load divided by the number of supporting ropes.

Front

If a load of 100 N is lifted with a pulley system, how much force is needed if there are two supporting ropes?

Back

50 N of force is needed to lift the 100 N load.

Front

What is the maximum static friction force?

Back

The maximum static friction force is the highest amount of friction that can be exerted before an object starts to move.

Front

What is the formula for calculating frictional force?

Back

Frictional force = coefficient of friction × normal force.