Work and Energy
The transfer of energy to an object by the application of a force that causes the object to move in the direction of the force.
What is work?
Any type of stored energy.
What is potential energy?
A crane uses an average force of 5,200 N to lift a girder 25 m. How much work does the crane do on the girder?
What is 130,000 J?
Energy cannot be created nor destroyed.
What is the Law of Conservation of Energy?
A quantity that measures the rate at which work is done or energy is transformed.
What is power?
The energy that an object has because of the position, or height from the surface of the Earth?
Hint: Three words
What is gravitational potential energy?
An apple weighing 1.5 N falls a distance of 2.0 m. How much work is done on the apple by the force of gravity?
What is 3.0 J?
If a system is closed, the mechanical energy is ___?.
What is conserved? (or constant)
What force must be balanced to climb up stairs?
What is weight?
The energy of an object due to the object's motion.
What is kinetic energy?
Weight
What is mass x acceleration due to gravity?
While rowing across the lake during a race, John does 3,960 J of work on the oars in 60.0 s. What is his power output in watts?
What is 66 W?
True or False: Potential energy can be transformed into kinetic energy and kinetic energy can be transformed into potential energy.
What is true?
The work done if 65 kg person rock climbs up a vertical cliff that is 7.0 m high.
What is 4459 J or 4500 J?
The amount of work an object depends on these two quantities.
What are force and displacement?
Gravitational Potential Energy
What is PE = mgh?
Calculate the gravitational potential energy of a 1,200 kg car at the top of a hill that is 42 m high.
Hint: acceleration due to gravity is 9.8 m/s/s
What is 490,000 J?
True or False: A boulder on top of a cliff has more potential energy than an acorn.
What is true?
A roller coaster has vertical drop of 65 m and a hill of 95 m. if the roller coaster has a mass of 250 kg, this is the speed at the bottom of the hill.
What is 36 m/s?
The total potential and kinetic energy of a closed system.
What is mechanical energy?
Kinetic Energy
What is KE = 1/2 mv^2?
A 35 kg child has 190 J of kinetic energy after he sleds down a hill. What is the child's speed at the bottom of a hill?
What is 3.3 m/s?
For any system, work done on the system increases or decreases the energy of the system.
What is the Work = Energy equation?