The Top Ten Things of Physics

Inertia

an object's non-wanting to change states (is measured by an object's mass). An example of inertia is the tablecloth trick

Ohm's Law

Ohm's law has to do with resistance. V=IR is the equation for Ohm's law. V= voltage, I= current, and R= resistance.

Units for V, I and R

Newton's 1st Law

An object at rest tends to stay at rest and an object in motion tends to stay in motion unless acted upon by an outside force.

Newton's 2nd Law

 acceleration is directly proportional to force, and is inversely proportional to mass. F=ma

Newton's 3rd Law

 “every action has an equal and opposite reaction.”

Action Reaction Pair: Hammer pushes nail down, Nail pushes hammer up

Speed and Velocity

You can accelerate while keeping the same speed only when going in a circle without changing speed. Cannot have changing speed and have constant velocity. Difference between velocity and speed is that v requires a specific direction and speed does not

Work/Power

For work to happen, force and distance must be PARALLEL!!
Example problem:

Equation: Work=(force)(distance)

Units: Joules (J)

Equation: Power=work/time

Units: Watts

If a 600N person walks up stairs that are 4 meters high, how much work is done?

Work=F*d

Work=600N*4m

Work=2400J

When is there more work? When a person goes up the stairs to third or when the elevator carries them to third?

The work required is the same. The upward force against gravity (or weight) is the same, and the distance that is parallel to that force (height) is the same, therefore work is the same. Horizontal distance does not matter because it is perpendicular to the upward force, and therefore contributes nothing to the work done.

When considering work, only the height matters.

Work happens to an object when force is exerted on that object over a distance. The equation for work is work=force*time, and it is measured in m/s or Joules. For there to be work, the force and distance must be parallel. In this example, the person's wright, or force, is vertical, and therefore for there to be work, the distance must be vertical as well. Work does not happen when the distance is perpendicular to the force, or when there is no distance.

If the force of the person is 4N, and the staircase is 15m tall, how much work will there be? 

work=force*distance

        = 4N*15m

work= 60 Joules

Power is how quickly work is done. The equation for power is Power=(work)/(time) and is measured in Watts.

If it takes the person 10 seconds to reach the top, how much power is exerted?

Power=(work)/(time)

=60J/10s

Power=6 Watts

Coulomb's Law

Coulomb's law states that the electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects.

Torque 

Torque is a measure of how much a force acting on an object causes that object to rotate. Torque is equal to the force multiplied by the lever arm. Torque IS NOT equivalent to force! Lever arm is the distance from the axis to the center of gravity. 

Conservation of Momentum

Individual objects can change their momentum, but systems cannot

Ptotal before=Ptotal after

Together in the Beginning:

m_av_a+m_bv_b = m_av_a+m_bv_b

Together in the Ending:

m_av_a+m_bv_b=m_a+bv_ab