11.3 Motion and Force

What are the four fundamental forces in nature?

Gravity, electromagnetic force, strong nuclear force, and weak nuclear force.

What is the weakest of the natural forces?

Gravity.

When two surfaces touch each other, there are always microscopic _________________ and __________________ that cause surfaces to "stick together."

Hills, Valleys

When there is a net force acting on an object, how does the object accelerate?

In the direction of the stronger force.

What is the friction that is present between two objects that are in motion?

Kinetic

When two or more forces are acting upon the same object at the same time, the combination of all the forces acting on the object is called the __________ force.

Net

What units are forces measured in?

Newtons (N)

What type of friction is present when two objects are stationary?

Static

_______________ friction is greater than __________________ friction.

Static, kinetic

Name two instances when friction is beneficial.

Striking a match and using velcro.

What is the strongest of the natural forces?

Strong nuclear force.

When there is a net force acting on an object , the object will accelerate in the direction of the greater force. In this case, the object has ______________________ forces acting on the object.

Unbalanced.

How can friction be reduced?

Using lubricants and low-friction materials.

What are the two ways through which forces act?

Contact and from a distance.

What type of forces require that objects do not touch each other?

Field forces.

What are the different kinds of kinetic friction?

Fluid, rolling, and sliding

What is the force that always opposes the motion of an object?

Friction.