Physics midterm 2

Topics 5 -7 ( Dynamics, Energy and Linear Momentum)

Forces are a measure of….

the interaction between objects

Inertia

opposing the change of motion

Net force

The vector sum of all forces applied to an opject

Newtons first law

selecting a set of inertia reference frames, that are observed from a body that is at rest or has constant velocity (no acceleration), no net force is acting on it.

If still means no force pushing

Newtons second law

The net force acting on a body is equal to the mass x the acceleration

Fnet = ma

Newtons third law

Body A exerts a force on body B. Body B also exerts an equal force in opposite direction on body A

F b on a = -F a on b

you push on something and it pushes back

Does force cause motion?

No, force causes acceleration or change in the state of motion.

Same reason we don’t count forces that are no longer touching the body in question

If an object is thrown as a projectile (e.g at an angle with the horizontal), does the “force of the throw” pushing it forward?

No, the object is no longer touching your hand so the force no longer counts. Force causes change in the state of motion not the motion itself

Force of gravity

Fg = mg

gravity is dependant on the mass of the object, its greater for the larger mass of the object

what is weight?

weight is gravities affect on mass

What is a reaction force

forces that arise in connection with some other interaction. Cuased by another force or other external condition

Normal force

force between 2 objects that are pushing on each other. Always perpendicular. Think newtons third law. You push on something and it pushes back

Friction

irregularies in the forces being contacted. 2 types of friction, kinetic and static.

kinetic friction is when

occurs when the object is moving

static friction is when

occurs when the object is static or not moving

Air resistance

the frictional force exerted by the air on a moving object

Tension

force inside a rope. Force by which a rope will pull on an object

Steps for drawing free body diagram

1. identify all the might exert a force on object

2. Identify newtons third law pairs (Fn)

3. Identify coordinates, F net = 0 and acceleration

4 basic forces

1. Gravitational

2. Electromagnetic

3. Stong (nuclear)

4. Weak

Conservation of energy