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29 Cards in this Set
- Front
- Back
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Inertia |
Tendency of an object to remain in its present state of motion
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Mass
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Quantitative measure of an object's inertia
How much that object will resist a change in motion Measure in kilograms (kg) |
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Weight
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Gravitational force an object experiences when near a much larger body of mass
Measured in newtons (N) Weight = mg Weight and mass are proportional, but are not the same physical quantity |
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Center of mass
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Single point of an object where mass is concentrated
Point through which a single force may be applied in any direction causing object to accelerate equally Does not always coincide with geometric center |
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Center of gravity
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Single point at which the force of gravity can be applied to the entire mass
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4 Forces in nature:
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1. Strong nuclear forces
2. Weak nuclear forces 3. Gravitational force 4. Electromagnetic force Only last 2 forces are tested on the MCAT |
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Contact forces
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Must act in at least 1 of 2 directions:
1. Perpendicular to surface (normal force) 2. Parallel to surface (requires friction) Exception is tension, which can act in any direction away from object Considered electromagnetic forces Something must be making visible contact with system Not do act at distance |
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Gravitational force
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F = mg
Act at distance |
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Electromagnetic force
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Requires charged object or a magnet
Act at distance |
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Newton's 1st law
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Law of inertia
An object in a state of rest or in a state of motion will tend to remain in that state unless it is acted upon by a net force |
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Newton's 2nd law
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F = ma
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Newton's 3rd law
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For every action there exist an equal and opposite reaction
Forces never act on same system |
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Newton's law of universal gravitation
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Every mass in the universe exerts an attractive force on every other mass in the universe
F = Gm1m2/r^2 G = 6.67e^-11 m^3 kg^-1 s^-2 Gives magnitude of force but not direction |
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Normal force (Fn)
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Force perpendicular to surface
Force of inclined plan pushing back against gravitational force Normal force of inclined plane: Fn = mgcos0 Normal force of curved surface: Fn = mgcos0 + mv^2/r (centripetal force) |
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Net force of incline plane (no friction)
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Fnet = mg + Fn
Fnet = mgsin0 Points directly along inclined plane |
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Circular motion
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Object spinning or moving in circles
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Centripetal acceleration
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Ac = v^2/r
Always points toward the center of circle that is circumscribed by motion Direction is always changing Magnitude is always constant |
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Centripetal force
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Fc = mv^2/r
Always points toward center of circle Must be created by another force Must be at least one of three forces: 1. Gravity 2. Electromagnetic 3. Contact |
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Acceleration down inclined plane
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a = gsin0
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2 Directions of contact force:
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1. Normal force (Fn) is always perpendicular to contact surface
2. Frictional force is always parallel to contact surface |
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Friction
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Cause by attractive molecular forces between contiguous surfaces
Opposes relation motion between surfaces |
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2 types of friction:
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1. Static friction (Fs)
2. Kinetic friction (Fk) |
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Static Friction
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Force opposing motion when 2 contiguous forces are not moving relative to each other
No sliding Fs = uFn |
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Kinetic Friction
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Force resisting motion once the 2 contiguous surfaces are sliding relative to each other
Yes sliding Fk = uFn |
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Coefficients of friction (u)
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Represent fractions of normal force that will equal static and kinetic frictional forces
Usually have a value less than 1 u(static) is greater than u(kinetic) |
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Drag
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Air resistance
Type of friction Fluid resistance to an object's motion through that fluid |
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Viscosity
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Type of friction
Fluid's resistance to motion through itself |
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Tension
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Force acting through a flexible object with no mass, such as a string or rope
Equal throughout rope as long as there is no friction acting on the rope At any point in rope, there is tension force pulling in equal and opposite directions, but only use force pulling away from system Replace rope with force vector acting on system |
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Hooke's Law
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Force due to a compressed or stretched object
Force applied by most objects against a deforming force F = -k(Xf - Xi) Negative sign can usually be ignored Usually refers to springs |
