Ch 3A/4 Forces and Dynamics#

Question 1

What is a force?

Answer 1

A force is a push or pull upon an object resulting from the object’s interaction with another object.

Question 2

What are the two broad categories of force?

Answer 2

contact force and non-contact force.

Question 3

State one example of a contact force.

There are at least 5 examples.

Answer 3

(Any one will do)
friction
tension 
normal force
air resistance 
applied force

Question 4

State one example of a non-contact force.

There are at least 3 examples.

Answer 4

(Any one will do)
gravitationa force
electrostatic force
magnetic force

Question 5

When all forces acting on an object is balanced, what can we deduce about the resultant force, F?

Answer 5

F = 0 N

Question 6

When forces acting on an object is unbalanced, what can we deduce about the resultant force, F?

Answer 6

F is not equal to 0 N

Question 7

What is a resultant force?

Answer 7

Resultant force is the product of the mass and the acceleration of the object and the direction of the force is the same as the object’s acceleration.

Question 8

What is the formula for resultant force?

Answer 8

F = ma

Question 9

Define weight. (on earth)

Answer 9

The weight of a body is the gravitational force exerted by Earth on the body.

Question 10

Define contact force.

Answer 10

The contact force is the force exerted by the contact surface on the body. It acts perpendicularly to the contact surface.

Question 11

Define tension.

This is an example of a contact force.

Answer 11

The tension force is the pull exerted by a stretched string, rope, cable or wire on an object attached to it.

Question 12

Define normal force.

This is an example of a contact force.

Answer 12

The normal force is a push exerted by a surface on an object. (The force acts perpendicular to the surface that an object contacts)

Question 13

Define friction.

This is an example of a contact force.

Answer 13

Friction is a force that resists the motion of objects in contact with each other.

Question 14

Define air resistance. (also known as drag)

This is an example of a contact force.

Answer 14

Air resistance is the friction between a moving object and the air it is moving through.

Question 15

Define magnetic force.

This is an example of a non-contact force.

Answer 15

The attractive or repulsive forces between magnets.

Question 16

Define electrostatic force.

This is an example of a non-contact force.

Answer 16

The attractive or repulsive forces between electric charges.

Question 17

Define gravitational force.

This is an example of a non-contact force.

Answer 17

The pull exerted by Earth’s gravity on any object.

Question 18

What is a free-body diagram?

Answer 18

A diagram which shows all the forces acting on a body.

example of a free-body diagram

Resultant force is excluded from the diagram.

Question 19

What is Newton’s First Law of Motion?

Answer 19

Newton’s First Law of Motion states that every object will continue in its state of rest or uniform motion in a straight line unless a resultant force acts on it.

This law shows how an object will behave when the resultant force acting on the object is zero.

Question 20

What is Newton’s Second Law of Motion?

Answer 20

Newton’s Second Law of Motion states that when a resultant force acts on an object of a constant mass, the object will accelerate in the direction of the resultant force.

This law shows how an object will behave when the resultant force acting on the object is not zero. This also give rise to the formula F = ma.

Question 21

What is Newton’s Third Law of Motion?

Answer 21

Newton’s Third Law of Motion states that if a body A exerts a force F on body B, then body B will exert an equal and opposite force F on body A.

examples of action-reaction pair of forces

The two forces that acts on different bodies are known as the action-reaction pair of forces.