Force and Work
What is the unit of Force?
Newtons (N)
What is the unit of potential energy?
Joule (J)
What is the unit of kinetic energy?
Joule (J)
How do you calculate mechanical energy?
Kinetic energy + Potential energy
What is efficiency expressed as?
A percentage
If mass stays the same, but I increase acceleration, what happens to the force?
Force increases
Potential energy is the energy of?
Stored energy
Kinetic energy is the energy of?
Motion
What is the 1st Law of Thermodynamics?
Energy cannot be created or destroyed, but only converted from one form to another
What is the 2nd Law of Thermodynamics?
No energy conversion is 100% efficient, waste energy will be produced and it's usually in the form of thermal energy
A water bottle is lifted 0.98 m with a force of 40 N. How much work is being done on the water bottle?
39 m
A waterfall is an example of what type of potential energy?
Gravitational potential energy
What is kinetic energy dependent on?
Speed and mass
If a snowboarder has 3000 J of potential energy at the top of the hill, how much kinetic energy will they have at the bottom of the hill?
3000 J
Describe the two forms of energy that come from the output energy of a system or object.
Useful energy: energy that performs the task
Wasted energy: energy that is not useful, often thermal energy
What does the area under the curve of a force versus distance graph tell us?
Area = Work
What is potential energy dependent on?
Mass and height
At what point in a pendulum swing is there only kinetic energy?
At the bottom of the swing
When we calculate the conversion from potential energy to kinetic energy or vice versa, what are we assuming?
That no energy is being lost through thermal energy or any other form of energy
In the example of a coal power plant, what type of energy conversions exist?
Chemical potential energy -> Thermal energy -> Kinetic energy -> Electrical energy
A 15 kg box moves with an acceleration of 2.01m/s2 [E] over a distance of 10m. How much work is being done on the box?
301.5 J -> 3.0 x 102 J
A hailstone with m= 0.71 kg is formed in a cloud 2.1 km high. How much gravitational potential energy does the hailstone have?
14626.71 J -> 1.5 x 104 J
A hockey puck has a mass of 0.30 kg. If the hockey puck has 52 J of kinetic energy, what is it's speed?
18.6189 m/s -> 19 m/s
Think back to the phet activity we did, what were two ways to increase the total energy of the system?
Increasing mass or height
If a lightbulb uses 130 kJ of electrical energy and emits 46 kJ of light, what was the efficiency of the light bulb?
35.384...% -> 35%