Vocab
When does "zero" work occur?
When an object is not moving
Energy of motion
What is kinetic energy?
A 500 kg roller coaster is traveling 7 m/s at a height of 25 m. Calculate mechanical energy.
134750 J
An apple falls from a tree. What kind of work is being done on the apple by gravity?
Positive
Energy stored in a compressed object.
What is elastic potential energy?
Work is positive when...
The force and displacement are in the same direction.
True
A 2.1 kg rock is being held at a height of 8.7 m. Calculate it's speed energy just before hitting the ground.
13 m/s
Kyle is pushing his physics book away from him across the table. Is work being done?
Yes
Stored energy is known as
What is potential energy?
True or False: Running and walking up the stairs require the same amount of work
True
What is mechanical energy?
A spring with a spring constant of 125 N/m is stretched to 1.7 m. Calculate its elastic potential energy if its rest position is 1.3 m.
10 J
A 1500 kg car is being pushed down a road at a speed of 1.4 m/s. How much work must be done to increase the speed to 1.9 m/s
1237.5 J
rate of doing work, and its units
what is power and watts?
(Assume masses are equal) JeVaunn and Aiden both lug their books up a flight of steps. JeVaunn get up there in 1 minute while it takes Aiden 1.5 minutes.
Who is more "powerful"?
JeVaunn
An object contains 200J of GPE. What is one change you could make to this object or it's surroundings to increase its GPE?
Increase it's mass
Increase it's height above the ground
Increase gravity (change to a planet with g greater than 9.8)
John is lifting a 7 kg bowling ball up from the 2nd floor to the third from over the railing a distance of 2.5 meters. What is the work done?
171.5 Joules
Denis' car is slowing down to a stop. Is this positive or negative work?
negative work.
Internal Energy is a measure of
What is heat/temperature
Simon uses a force of 1000 Newtons to push a fridge a distance of 10 meters in 5 seconds. How much power is exerted?
2000 W
When energy in a system is "lost", it commonly transforms into heat. This indicates that what external force is present?
Friction/air resistance
Your family is moving to a new apartment. While lifting a box 1.5 m straight up to put it on a truck, you exert an upward force of 200 N for 1.0 s. How much power is requried to do this?
300 W
Steph is carrying her book across the room by balancing the book steady on her hand. Is work being done on the book?
No