AP Physics C/Printable version
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Motion in One Dimension
Scalars vs. Vectors
edit- Scalars
- measurements that have no direction to them
- Examples: Distance, speed
- Vectors
- measurements that have a direction to them
- Examples: displacement, velocity
Displacement vs. Distance
editDisplacement - the most direct route from one point to another. (The net distance traveled)
Distance- the length traveled
Example Problem:
If a car travels 3m directly east then 5m directly west, what is the displacement and what is the distance traveled?
Displacement: if a car goes 3m east, and then it goes 5m opposite of east, the car will travel enough to cancel out the 3m east traveled, and go an extra 2m after that. This is best represented in an equation:
If east is positive:
=3m (east) + 5m (opp. east)
=3m (east) + (-5)m east
= -2m east
= 2m west
Displacement is often represented by the variable s, or x.
Velocity vs. Speed
editSpeed- change in distance over change in time
Velocity- the change in displacement divided by the change in time. It is also defined as the derivative of the displacement equation. Velocity is a vector.
Vectors and Motion in Two Dimensions
Vectors in 2D
editVectors in 2 dimensions have both an x and a y component. We can find the components if given an angle, θ, in the following manner:
Projectile motion
editProjectile motion is one of the most common applications of 2D vectors. Lets start with an example, lets say we throw a ball 30 m/s at a 60° angle. We can figure out how far it will land and how long it will take. The acceleration in the y of a projectile motion question is always . Since velocity is the integral of acceleration, , and C will always be equal to initial velocity, .
IMPORTANT: Any projectile with an initial height or y of 0 will reach the apex of its height at (where t is the total time of travel). This is because at the apex, the slope of the tangent line to the y position is equal to zero.
So lets solve for time.
From here we can solve for the range of the object.
Electric Charge
Fundamentals of Electric Charge
edit- Intrinsic to fundamental particles
- 2 types: positive (+), negative (-)
Positive - Lack of electrons Negative - More electrons No charge = Neutral
Same charges repel: + and + or - and - Opposite charges attract: + and -
- Coulomb: Measurement of the amount of electric charge (similar to moles in chemistry)
Atomic Particle | Mass | Charge |
---|---|---|
Neutron | 1.675 * 10^{−27} kg | 0 C |
Proton | 1.673 * 10^{−27} kg | 1.602 * 10^{−19} C |
Electron | 9.11 * 10^{−31} kg | -1.602 * 10^{−19} C |
Atomic Notation
edit
- A = Atomic mass = # protons + # neutrons
- Z = Atomic Number = # protons
- E = element symbol (like U for Uranium)