Energy

Doubling mass causes potential energy to _______________, and kinetic energy to go up by _________. Look at the potential energy equation - Mass is in there one time on the right, so if it doubles, the answer on the left… DOUBLE TWO (it also doubles) Now look at the KINETIC energy equation - Like with potential energy mass is in there one time on the right (just one time), so if it doubles, the answer on the left goes up by …

Doubling velocity causes potential energy to _______________, and kinetic energy to _______________. Look at the potential energy equation - Velocity is nowhere in the potential energy equation, so if it doubles it causes potential energy to …. Do Nothing Go up by 4 !!! Now look at the KINETIC energy equation - Not like with mass, here velocity is squared (^2), so if it doubles, the answer on the left …. Why? – 2 2 (2 squared) is 4 !!

Doubling the height causes potential energy to _______________, and kinetic energy to _______________. Look at the potential energy equation - Height is in there one time on the right, so if it doubles, the answer on the left… Double Do absolutely nothing (NOT CHANGE) Now look at the KINETIC energy equation - Where is height in this equation?? Height only affects E p, not E k !! If it’s not here, it must not have any affect, so…. Nowhere!

Mass: Weight: Velocity: Height: Energy: kilograms - kg newtons - N meters per second - m/s meters - m joules - J It is a force, F w A newton-meter

Energy carried by electromagnetic waves Example: Light Example: Radio Example: Microwaves (including sunlight)

Energy stored in an object that is stretched or compressed. Example: a stretched rubber band Example: a stretched spring Example: a compressed spring Example: something bent (like a plastic spoon) that may spring back)

Energy stored in the bonds between atoms or molecules. Example: food Example: gasoline for a car Example: wood or oil that can burn Example: chemicals in a battery Example: gunpowder

Energy stored because of the position of an object above the earth. Example: a car on a hill Example: a rock on the edge of a cliff Example: a baseball in the air after it is thrown

The energy associated with a moving object, or “the energy of motion.” Example: a rolling ball Example: a moving car Example: a flying bird Example: a canon ball (after firing)

The energy stored by separated charged particles. Example: a battery Example: a generator Example: static electricity (this could also be considered chemical, since that’s what batteries are made of)

The overall kinetic energy of moving particles We can use thermal energy Example: Steam to turn a turbine (All things have thermal energy except at a temperature of absolute zero) Thermal energy can also be considered a waste product… more on that in the next slides. We measure average kinetic energy with a thermometer, and call it temperature

After a transformation, the energy of a system is always ___________. (more/less/the same) During transformations between mechanical forms of energy, _________ causes some energy to be converted into ________. the same friction heat Examples: Brakes on a car A ball on a rough surface Rubbing hands together usually a waste

A man lifts some bricks on a ladder to a height of 2 meters using 80 joules of energy. What is the mass of the bricks?

How high do you have to lift a 10 kg rock to raise its potential energy by 200 joules?

What is the kinetic energy of a cannon ball that has a mass of 8 kg and a velocity of 150 m/s?

What is the potential energy of a diver on a high-dive if his mass is 75 kg and the height of the diving board is 15 meters?

How high will a ball go if it has a mass of 0.2 kg is thrown with a velocity 30 m/s?

A rock falls from a cliff from a height of 20 meters, and strikes the ground with an energy of 3000 joules. What was the mass of the rock?