Unit 2 - Dynamics

Question 1

What is a force?

Answer 1

• A push of pull
• Vector quantity
• Measured in Newtons (N)

Question 2

Non-contact forces

Answer 2

Gravitational forces, magnetic forces and static electric forces existing even when the objects aren’t in contact.

Question 3

Contact forces

Answer 3

Forces exist because of a push or pull through direct contact are called contact forces

Question 4

Newton’s First Law (Law of Inertia)

Answer 4

If no net force acts on an object, it maintains its current state of motion.

Question 5

Inertia

Answer 5

The tendency for stationary objects to stay stationary and moving objects to maintain their state of motion is called inertia.

Question 6

Newton’s Second Law

Answer 6

When Fnet is not equal to zero. It stands to reason that if there is an unbalanced force acting on an object, it will cause the object to accelerate. It is also intuitive that the acceleration will have the same direction as the net force.
Fnet=ma

Question 7

Newton’s Third Law

Answer 7

For every action there is an equal and opposite reaction. If object A exerts a force on object B, then object B will exert a force back on object A of equal magnitude, but in the opposite direction.

Question 8

The normal force

Answer 8

Any time an object pushes on a surface, the surface pushes back according to Newton’s 3rd Law. The perpendicular part of this force between the object and the surface is called a normal force.

Question 9

Sliding friction

Answer 9

Sliding friction acts to oppose 2 surfaces sliding past each other.

Question 10

Static friction

Answer 10

For a given object on a given surface, there is a max. static frictional force that must be overcome before the object will start to slide.

Question 11

Kinetic friction

Answer 11

Our simple model of kinetic friction stays that once surfaces sliding past each other, friction provides a constant force. This force will not depend on the speed of the object!

Question 12

Mass

Answer 12

Mass is relative to the amount of matter that makes up an object. This property will remain the same on earth or in space.
Measured in kg

Question 13

Weight

Answer 13

Weight is actually a force! Your weight is the force of gravity acting on you
Measured in N

Question 14

Apparent weight

Answer 14

Apparent weight is how you “feel”. This is the total upward force being exerted on you. Generally, this will be the normal force acting on us.

Question 15

Hooke’s Law

Answer 15

F is directly related to ΔX

*Assume strings don’t stretch and that the mass=0!!