Energy Basics
Define Energy and give an example
Energy is the ability to do work, or cause a change. Examples may vary
Name 3 types of energy and give an example
Examples may vary
What is “work” in physics, and how is it different from power?
Answer: Work = force × distance . Power =work over time
Name 2 examples of simple machines
answers may vary
What happens to potential and kinetic energy when a basketball rolls down a ramp?
Potential energy decreases as kinetic energy increases.
What is the law of conservation of energy?
Energy cannot be created or destroyed, only transformed from one form to another.
What is elastic potential Energy? Give an example
Energy stored when an object is stretched or compressed- rubber bands, bouncy balls.
What formula is used to calculate work?
Answer: W=F×d (Work = Force × Distance)
How does an inclined plane reduce the force needed to lift an object?
It spreads the work over a longer distance, requiring less force to move the object upward.
How do friction and air resistance affect the energy of moving objects?
They convert some kinetic energy into thermal energy, slowing the object down.
Kinetic energy is motion, and potential energy is stored energy due to its position
How does chemical energy differ from mechanical energy?
Chemical energy is stored in chemical bonds, and mechanical energy is the energy of movement.
How would you calculate the power of a motor that does 500 J of work in 5 seconds?
P=W/t=500J/5s=100W
Explain how a pulley can change the direction of force.
A fixed pulley lets you pull down to lift up; it changes the direction but not the amount of force.
Explain how energy transformations occur in a hair dryer or blender.
Electrical → mechanical (fan/blades) + thermal (heat) + sound.
If you were to put toast in a toaster, lower it down and let it toast, what would be the energy transformations occuring?
Kinetic- lowering the toast
electrical to thermal- the range heating up
radiant energy- the grill heating up.
kinetic energy- the toast popping up.
Explain the energy transformations occurring when flinging a rubber band across the room. Starting with an unstretched rubber band
Mechanical, stretching the band, elastic potential in the stretched band, mechanical energy as it is released.
Two students climb the same stairs, but one runs and one walks. Who has more power, and why?
The runner has more power because the same work is done in less time.
Describe the three classes of levers and give a real-world example of each.
1st class: Fulcrum in middle (seesaw)
2nd class: Load in middle (wheelbarrow)
3rd class: Effort in middle (fishing rod, tweezers)
Create or describe an energy transformation diagram for a wind turbine.
Kinetic (wind) → mechanical (blades) → electrical (generator) → thermal (small losses).
Why is a perpetual motion machine impossible?
Some energy is always lost as heat
Describe all the energy transformations that happen when a car drives up hill, slows, rolls down, and stops.
Driving up: Chemical → kinetic → gravitational potential
Slowing: Kinetic → thermal (brakes)
Rolling down: Potential → kinetic
Stopping: Kinetic → thermal (friction/brakes)
A 60-kg student climbs a 3-meter staircase in 4 seconds. Calculate the work done and power exerted.
W=mgh=60×9.8×3=1,764J
P=1,764/4=441 WP = 1,764 / 4 = 441 \, WP=1,764/4=441W
Compare a fixed pulley and a movable pulley in terms of force and distance trade-off.
Fixed pulley: Changes direction only.
Movable pulley: Reduces required force but you pull more rope (greater distance).
Analyze the total energy changes in a slide from start to finish, including friction losses.
At the top: Max potential energy
Going down: Potential → kinetic
At the bottom: Max kinetic energy
Throughout ride: Some energy → heat and sound due to friction