Definitions
Math
Types of Energy
Concepts
Review
100
The ability to do work.
What is Energy?
100
A child rolls his ball (m= 125 kg) down a sidewalk. If the ball starts rolling at 2.5 m/sec and rolls to a stop, how much work did friction do the entire time that the ball was rolling?
.39 J
100
Define Kinetic energy.
Energy in motion.
100
When friction takes energy from an object, where does the energy go?
Heat
100
Give the equation for Centripetal force.
m x v^2/ r
200
Work is the application of force over this.
What is distance?
200
A 2.3-KG wooden block slides across a carpenter shop's floor. If the floor is level and the block stops after traveling 3.5 m, what was its initial speed? (coefficient of friction is 0.52)
6 m/sec
200
Define potential energy.
Energy that is stored up, ready to work.
200
If you are trying to drag a very heavy, but short box using a rope- what is the best physical position for you to be in?
Crouched so that the rope is being pulled parallel with the top of the box.
200
Give the equation for torque.
Perpendicular force x r
300
Chemical energy is energy associated with the chemical bonds of these.
What are molecules?
300
A janitor pushes a box 11.1 m across the floor in 2.4 minutes. He exerted 67 N of force. How much power has he exerted?
5.1 Watts
300
Imagine a ball (12 kg), sitting on the edge of a cliff, when a sharp gust of wind going 35 m/sec pushes it off the cliff. When will the potential energy be the greatest? The Kinetic energy?
1. Before is starts moving. 2. Just before it hits the ground.
300
What is the first law of thermodynamics?
Energy can neither be created nor destroyed- only transferred.
300
The difference between centripetal force and torque
Centripetal force is a necessary force for all circular motion; torque is the force necessary for inducing circular motion.
400
This is energy associated with the motion (or potential motion) of charged particles.
What is Electrical energy?
400
A 345-gram ball rolls down a 3.1-m hill. If it started from rest and gets to the bottom with a speed of 4.2 m/sec, how much work did friction perform?
7 J
400
Explain how the potential energy of an object changes based on the system you're considering.
The system could have different heights.
400
Is it ever possible for the work done by friction to increase the kinetic energy of an object? Why or why not?
No- friction, by definition, opposes motion.
400
Give the equation for the Universal Law of Gravitation.
m(1) x m(2) x G/r^2
500
This is energy associated with the movement (or potential movement) of objects.
What is Mechanical energy?
500
a machine must move an object 15.1-m by exerting a 121 N force. If the machine must get the job done in 2.3 min, how much power must the machine's motor provide?
13 Watts
500
Explain why Potential Energy is measured in Joules.
PE= mgh. h is measured in meters. g is measured in meters/sec^2. m is measured in kg. Therefore PE is measured in (kg x m^2)/ sec^2. However a Newton is equal to (kg x m)/sec^2. So PE is measured in Newtons times meters- which is work. Work is measured in Joules.
500
What is the difference between power and energy?
Power is how much energy is done in a certain amount of time.
500
What is the Conservation of Momentum?
The total momentum within a system cannot change.
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