Princeton Review MCAT Physics Ch 5
What is the formula for centripetal force?
F=ma or F=mv^2/r
What does centripetal mean?
(To seek the center) Uniform circular motion always points towards the center of the circle
Translational equilibrium
If forces cancel out (Fnet=0, then translational acceleration is 0)
When does an object executing uniform circular motion?
If the speed is constant in a circular path
Rotational equilibrium
If torques cancel (Torque net = 0, then rotational equilibrium is 0)
What is static equilibrium?
If velocity is 0
Why doesn't an object fall towards the center of a circle if it is being acted on by centripetal force?
It is falling towards the center, but the speed of the object keeps it in orbit around the center
How would the net force on an object undergoing uniform circular motion have to change if the object's speed doubled?
It would quadruple as it is proportional to the square of speed
What is torque?
Measure of a force's effectiveness at making an object spin or rotate (measure of a force's effectiveness at making an object accelerate rotationally)
What is the unit for torque?
N*m
Can forces with no torque change the rotational speed of an object?
No
If something is in equilibrium, does that mean it has 0 velocity?
No as long as the velocity remains constant
Can you have acceleration without force?
No as per Newton's Second Law F=ma
Does acceleration affect speed in a circular motion
No. Acceleration changes the direction of velocity, not the speed
Rotational inertia
Object's resistance to rotation
What would rotate more easily: a hollow ball or solid ball?
Solid ball as it has a smaller rotational inertia and its mass is closer to the center of rotation
What happens if equilibrium is stated but not specified?
System is in both translational and rotational equilibrium
What is a pivot point or fulcrum?
The center of an object that does not move while the rest of the object moves
What determines an object's rotational inertia?
The farther away the mass is from the axis of rotation, the greater the rotational inertia will be
What is centripetal force?
The net force directed towards the center of a circle to cause it to execute uniform circular motion
Can the center of mass be located outside the object's matter?
Yes. Center of mass for a ring is inside the ring where no ring matter is located
What is the formula for magnitude of centripetal acceleration?
a=v^2/r
If we know lever arm, what is the equation for torque?
torque = lever arm * force
What is the equation for torque?
torque = rFsin(theta)
For torque, if r is perpendicular to the force, then...
torque = radius * Force
All systems that can spin or rotate have a center of...
turning
In physics, what does equilibrium mean?
0 acceleration
If presented with a center of mass problem where the object is multidimensional, how should you handle it?
Break it down into simple dimensions then apply the formula.
When is net torque 0?
Only when the total counterclockwise torque balances the total clockwise torque
What is the center of mass/gravity?
The one point that behaves as if the object were a single particle Place where all mass of an object is concentrated
Where does the direction point for velocity in a circle?
Towards the center (it is tangent)
What is the formula to find the center of mass along a wire?
Xcm = m1x1 + m2x2... /m1 + m2 ...
Why does velocity not matter for uniform circular motion?
Velocity is speed AND direction, and therefore the velocity would not be constant
If something produces a counterclockwise torque, is net torque 0?
no
