Work and Machines
Conservation of Energy
Efficiency and Power
Work and Energy Formulas
Misc
100
In the picture of the crowbar, which letter shows the fulcrum?
B is the fulcrum
100
Energy is measured in units of:
joules
100
The efficiency of a machine is usually expressed in:
percent
100
The equation used to calculate work when force is applied to move an object some distance is:
Work = force x distance
100
The action that would require NO work to be done is:
holding a 100-pound object over your head
200
In the picture of the crowbar, which letter shows the input force?
C is the input force
200
Kinetic energy increases with:
mass and speed
200
A unit used to measure power is the:
watt
200
If the mechanical advantage of a simple machine is 5, then:
the output force is 5 times greater than the input force
200
The brakes on an automobile become hot when they are used continuously because:
kinetic energy is being converted to thermal energy
300
According to this image, if the output force of a lever is located between the fulcrum and input force, the lever is a:
second class lever
300
Potential energy is energy due to the:
height of an object
300
Jake, who weighs 680 newtons, climbs a 6-meter ladder in 8 seconds. What was Jake’s power?
510 watts
300
Natalie lifts a 15-kg rock from the ground onto a 1.5 meter high wall. What is the amount of potential energy she has given the rock?
220 joules
300
A student lifts a 5 kg textbook 2 meters straight up. If gravitational acceleration is 9.8, how much work is done?
98 joules
400
Which of the following use the same units of measurement?
Energy and work
400
When energy in a system is transformed, what happens to the total amount of energy in the system?
It stays the same
400
An electric food processor uses 250 joules of electrical energy every second. Due to friction and other causes, the energy available to spin the blades to cut food is reduced to 200 joules per second. The efficiency of the food processor is:
80%
400
What is the kinetic energy of a go-cart with a mass of 150 kilograms and a speed of 20. m/s?
30,000 J
400
A machine does 300 joules of work in 15 seconds. What is its power output?
20 watts
500
Running up a flight of stairs, Marita generates 450 watts of power. If it takes her 6 seconds to go up the stairs, the amount of work she does in running up the stairs is ____ joules.
2,700
500
Describe the Law of Conservation of Energy?
Energy cannot be created or destroyed, only transformed from one form to another
500
Define power.
The rate at which work is done
500
Kevin jumps straight up in the air to a height of 1 meter. At the top of his jump, he has potential energy of 1,000 joules. Answer the following questions based on these numbers.
What is Kevin’s weight?
1,000 newtons
500
Which form of energy transformation occurs when a ball rolls down a hill?
Potential energy to kinetic energy