Energy/Conservation of Energy
Mechanical energy is the total amount of kinetic and _____ energies in a system
What is Potential?
What is required for work to be done?
What is an object moving in the same direction as the force applied?
What is the formula to calculate power?
What is work divided by time? What is force x distance over time?
Explain why adding oil to the moving parts of a machine increases its efficiency.
What is efficiency is increased when friction is decreased?
Gears are a modified version of what simple machine?
What is a wheel and axle?
Energy that is stored is ______ energy
What is was 2.4 Joules?
W = F x D = (12 N)(2m) = 2.4 Joules
A weightlifter bench presses 1000 N barbell 2 meters in 3 seconds. How much power was used?
What is 666.67 watts?
P = w / t = 2000 J / 3s = 666.67 watts
What is input work and output work?
Swinging a baseball bat is an example of a ______ lever.
What is third class level?
Identify three forms of potential energy.
d = W/F = 12000 J / 80 N = 150 m
What is the unit power is measured in?
What is Watts?
Describe at least two ways machines make work easier.
State the six simple machines.
What is lever, pulley, screw, wedge, wheel & axle, and inclined plane?
The amount of kinetic energy a moving object has depends on its ______ and its _______.
What is Mass and Velocity?
What is 700 J?
Work = F x D = 70 N x 10 m = 700 J
Daily Double (2 Parts) : You use a bar that is free to pivot about a fixed point to lift up your car. What is the name of the bar? Part 2 - You use lift your 1500 N car 2 meters in 1 minute. How much power did you expend?
What is a lever? What is 50 Watts?
Power = W / t = (1500 N x 2m) / 60s = 3000 J/60m = 50 Watts
The efficiency of a machine is always _____ 100 percent.
What is less than?
What simple machines can be classified as a lever?
What is a wheel and axle, and a pulley?
In the equation W(in) = W(out) what does each stand for?
What is work input, and Work output?
Daily Double: A tired squirrel (mass of approximately 1kg) does push-ups by applying a force to elevate its center-of-mass by 5cm in order to do a mere 0.5 Joules of work. If the tired squirrel does all this work in 2 seconds determine its power.
What is 0.25 Watts?
Power = Work/time = 0.5 J / 2 s = 0.25 Watts
Suppose your lawn mower was rusty. Of your 250,000J of work, only 100,000 go into cutting the lawn. What is the efficiency of the lawn mower now?
Identify and describe 3 simple machines in a car.
What is a wheel and axle, what is a pulley, what is a lever, what is a screw, what is an inclined plane?
Examples:
- Wheel and axle - wheels, steering wheel
- Pulley - Engine drive belt
- Screw - Bolts in the wheels, knobs on the radio or AC unit, windows
- Inclined Plane - Hood and windshield of the car
- Lever - Doors, hand break