Show:
Energy/Conservation of Energy
Work
Power
Using Machines
Simple Machines
100

Mechanical energy is the total amount of kinetic and _____ energies in a system 

What is Potential?

100

What is required for work to be done?

What is an object moving in the same direction as the force applied?

100

What is the formula to calculate power?

What is work divided by time? What is force x distance over time?

100

Explain why adding oil to the moving parts of a machine increases its efficiency.

What is efficiency is increased when friction is decreased?

100

Gears are a modified version of what simple machine?

What is a wheel and axle?

200

Energy that is stored is ______ energy

What is potential?
200
A bowling ball weighing 1.2 Newtons is lifted 2 meters. How much work is done?

What is was 2.4 Joules?

W = F x D = (12 N)(2m) = 2.4 Joules 

200

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 

200
The work done TO a machine is the _____ work, whereas the work done BY the machine is the ____ work. 

What is input work and output work?

200

Swinging a baseball bat is an example of a ______ lever.


What is third class level?

300

Identify three forms of potential energy.

What is chemical, gravitational, and elastic?
300
A lawn mower is pushed with a force of 80 N. If 12,000 J of work is done, what is the total distance the lawn mower was pushed?
What is 150 meters?


d = W/F = 12000 J / 80 N = 150 m

300

What is the unit power is measured in?

What is Watts?

300

Describe at least two ways machines make work easier.

What is increase force, increase distance force is applied, or change direction of force?
300

State the six simple machines.

What is lever, pulley, screw, wedge, wheel & axle, and inclined plane?

400

The amount of kinetic energy a moving object has depends on its ______ and its _______.

What is Mass and Velocity?

400
The amount of work required for a dump truck to move a mound of dirt 10 meters using a force of 70 Newtons is what?



What is 700 J?

Work = F x D = 70 N x 10 m = 700 J

400

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

400

The efficiency of a machine is always _____ 100 percent.

What is less than?

400

What simple machines can be classified as a lever?

What is a wheel and axle, and a pulley?

500
Energy stored in a loaded slingshot is _______ potential energy.
What is elastic?
500

In the equation W(in) = W(out) what does each stand for?

What is work input, and Work output?

500

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 

500

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?

What is 40%?
500

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