Definitions
What is Energy?
The ability to do work
A ball with a radius of 20cm is rolling down an incline at 5 m/s. what is its rotational velocity?
ω=v/r
25 rad/s
What is the SI unit for 𝜏?
N*m only
What are the forces experienced by roller-coaster riders in a loop-de-loop?
Force from the roller-coaster
Centripetal Force caused by Gravitational Force
Which has higher impulse on collision, a basket ball or a base ball? (assume they have the same mass)
The basketball because it bounces causing an addition of velocities
If a force is parallel to displacement, what does it do?
Work
If a bowling ball is rolled down a smooth bowling lane with 15 N of force and it rolls 18 m, what is the work done?
W= F*d -> 270 J
What is the SI unit for W?
Joule
A pickup truck and a slug bug are going the same speed. Which vehicle would have greater momentum?
The pickup truck would have greater mass but equal speed making it's momentum larger than the slug bug p=m*v
At what point in it's swing does a pendulum have the greatest potential energy, and when does it have the greatest kinetic energy?
At either side when the height is the greatest it will have the greatest potential energy
In the middle of it's swing when the string is perpendicular to the ground is when it would have the highest kinetic energy
What 2 statements must be satisfied for an object to be in equilibrium?
1. Fnet=0
2. 𝜏net=0
A car with a mass of 1500 kg hits a wall at 20 mph, and takes 0.1 seconds to come to rest. What was the average force experienced?
Ft=change in p (aka m*v)
F=m(vf-vi)/t
F=133,333 N
What is the SI unit for ω?
rads/sec
What forces are active on a satellite orbiting Earth?
Gravitational force only meaning they are in free fall
The gravitational force creates a centripetal force; satellites need a large tangential velocity to stay in orbit
When moving closer to the center of a carousel, what changes and why?
The radius becomes smaller, which in turn makes your tangential or linear velocity lower. Angular velocity stays the same on all parts of the carousel.
vtan=r*ω
What is a Nonconservative Force vs a Conservative Force, and what are examples of each?
Nonconservative: E cannot be regained
Ex: Friction
Conservative: E can be regained by returning to original state
Ex: Gravity, Elastic
If I took the merge ramp with a radius of 15m on my way here today at 35mph in my car that weighs 1500 kg, what was the centripetal acceleration experienced?
1 mi= 1.6 km
ac=v2/r
ac=16.4 m/s2
What is 30 degrees in rads?
360 deg=2pi rad
30 deg= 0.524 rad
You push down on one end of a see-saw to lift your friend and then let them return to the ground. If you apply the same force closer to the pivot point, would they be raised higher or lower?
They would be raised lower than before, because less torque would be produced
𝜏 = F*distance from pivot point
Can a centripetal force do work?
No, because it will always be perpendicular to the velocity
What are Kepler's laws?
1st Law: Planets have an elliptical orbit around the sun
2nd Law: The line from the sun to a planet sweeps out equal areas of space for equal time intervals.
3rd Law: The square of the orbital period of a plant is directly proportional to the average distance of the planet from the sun
When tightening a bolt, you push perpendicularly on a wrench with a force of 165 N at a distance of 0.140 m from the center of the bolt. How much torque are you exerting (relative to the center of the bolt)?
𝜏= F*distance from pivot point
𝜏= 23.1
What is the SI unit for momentum?
p=mv
kg*m/s aka Ns (Newton Second)
An elastic collision between a cue ball and a pool ball occurs. Initially the cue ball moves with speed v, and the pool ball is at rest. After the straight on perfectly elastic collision, what is the cue ball's final speed as well as the pool ball's?
Cue ball final v = 0
Pool ball final v = v
Due to Conservation of Momentum and Kinetic Energy
When an ice skater is rotating and brings her arms inward, what changes and why?
It lowers her rotational inertia since her mass is closer to the axis of rotation. This makes her rotational velocity increase in order to conserve angular momentum
L=ω*I