Vector or Scalar?
- a vector quantity that is experienced as pushing or pulling on objects.
- N = kg*m/(s^2)
What's the difference btw mass and weight? Define both and give their SI units.
Mass (kg) is a scalar quantity that measures body's inertia (the amount of matter in something).
Weight (N) is a vector quantity and measures gravitational force (usually that of earth's) on an object's mass.
Equation of weight
Does gravity increase or decrease as we get closer/farther from earth?
Gravity (g) increases the closer we get to the earth's center of mass. Near the earth's surface g~10m/s^2
Newton's 1st Law (or Law of Inertia)
A body either at rest or in motion with constant velocity will remain that way unless acted upon by a net force.
Newton's 3rd Law (law of action and reaction)
- To every action there is always an opposed but equal reaction.
If you see force on MCAT problems do these two things:
- 1. Think acceleration. and if you see acceleration think force.
- 2. Draw free body diagram (if forces are not in just one direction, break them down into x and y components)
Gravitation force formula
- Where G=6.67*10^(-11) universal gravitational constant
Define translational, rotational and circular motions
translational motion occurs when forces cause an object to move without any rotation.
rotational motion occurs when force is applied so that the object rotates around a fixed pivot point, aka fulcrum.
circular motion occurs when forces cause an object to move in a circular pathway.
What's torque? Definition & formula.
In rotational motion, application of force at some distance from the fulcrum,along the lever arm, creates torque.
Forces in circular motion are resolved in radial and tangential components. Describe each.
radial is center-seeking and tangential is on the tangent/side. In uniform circular motion, the tangential force is zero (there is no change of speed of the object).
centripetal force -- definition and formula.
centripetal force is the radial force (directed towards the center).
Centripetal acceleration -- formula, direction, definition.
Centripetal acceleration is a~ generated by centripetal force that keeps objects in its circular pathway.
Acceleration is always in the same direction as the force (twrds the center in this case).
Give an example of Centripetal Force/Acceleration problem
Force of gravity that maintains a satellite's orbit. Or a tension in rope attached to an object that is spun around.
Friction. Definition, direction.
Friction is a kind of electromagnetic force that works to oppose the movement of objects.
Usually directed opposite of an object's movement and causes it to slow down or stop.
Static Friction -- Definition and formula
- Static Friction exists btw stationary object and the surface upon which it rests.
Normal force -- definition and direction
- Normal force is a component of a contact force that is perpendicular to the plane of contact between the object and the surface upon which it rests.
Which one is bigger: kinetic or static friction?
max value of Static Friction is always greater than value of kinetic friction.
- Kinetic Friction exists btw sliding object and the surface upon which it slides.
- (μk,instead of μs)
If net force is zero, what can you say about the values of velocity and acceleration?
Velocity is either zero (object is stationary) or non-zero constant (moving at a constant velocity).
Net acceleration is zero.
What's translational equilibrium?
translational equilibrium occurs when vector sum of net forces is zero.
What's rotational equilibrium?
rotational equilibrium occurs when vector sum of net torques is zero.