Work
What is the transfer of energy that occurs when a force causes an object to move over a distance, and what is its equation?
Work; W = F x d
What is the formula for Power and what is its unit?
Power equals work divided by time. Unit = Watt
What is the formula used to calculate Gravitational Potential Energy (GPE)?
GPE equals mass, multiplied by gravity, multiplied by height. GPE = m x g x h
What is the formula for kinetic energy?
KE = 1/2 x m x (velocity squared)
What is the unit for both work and energy?
Joule
A student pushes on a stationary brick wall with 200 N of force for 60 seconds. How much work is done on the wall?
0 Joules
200 Watts
A 2 kg textbook sits on a shelf 4 meters above the floor. What is its GPE?
80 Joules
What is the kinetic energy of a 3 kg bowling ball rolling at 4 m/s
24 Joules
What does the Law of Conservation of Energy state?
Energy cannot be created or destroyed; it can only be transformed from one form to another.
How much work is done to lift a 4 kg box straight up at a constant speed to a height of 3 meters?
120 joules
A student carries a 40 N backpack up a 1.5 m stairwell in 3 seconds. What is the student's power output?
20 Watts
What form of potential energy is stored in chemical bonds and released during cellular metabolism or burning fuel?
How many times greater is the kinetic energy of a ball if its speed is doubled?
4 times greater
A machine is 75% efficient. What percentage of energy input contributes to useful work. What happens to the rest of the energy?
75%, The rest of the energy is lost to heat/friction.
It is the same.
On Monday, a student gets to school early and walks up a flight of stairs to get to class. It takes the students 15 seconds. The next day (Tuesday) the student is late to class so he runs up the flight up stairs in 5 seconds. On which day does the student do more work? On which day does the student use more power?
Work is the same for both days. The student uses more power on Tuesday.
When an textbook is lifted 2 meters above the ground it gains 10 J of potential energy. How much force was required to lift the textbook?
5 Newtons
A 2 kg cart moving at 4 m/s is brought to a complete stop by braking over a distance of 2 meters. What force is required to stop the cart?
8 Newtons
What are 6 types of simple machines? Can they output more work than is input?
Lever, screw, pulley, inclined plane, wedge, wheel and axle.
No, machines don't multiply work, they trade-off force and distance to make work easier!
A 5.0 kg block is pushed across a horizontal floor with a forward force of 25 N over a distance of 3.0 m against a friction force of 5 N. What is the net work done on the block?
60 Joules
How much force is required to move an object 50 meters in 10 seconds with a power output of 70 Watts?
14 Newtons
A 70 kg cliff jumper stands on a ledge 20 meters above a lake. Using conservation of energy, what will the jumper's final velocity be right before hitting the water?
20 m/s
A skateboarder going 4 m/s has 40 Joules of kinetic energy. How much kinetic energy does she have if her speed increases to 8 m/s?
160 Joules
A student uses a pulley system to lift a 120 N box a height of 1.5 m by pulling with a force of 50 N over a distance of 4 m. What is the efficiency of the pulley system?
90%