Vocab
A man carries a briefcase while walking toward his plane. Is he doing work on the briefcase?
No
A 7 kg object is motionless. Calculate 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 or negative)
Positive
Energy stored in a compressed object.
What is elastic potential energy?
Work is positive when...
Energy is added to a system
True
A 2.1 kg rock is being held at a height of 8.7 m. Calculate it's kinetic energy just before hitting the ground.
179 J
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
True or False. (Assume masses are equal.) You and me both lug our books up a flight of steps. You get up there in 1 minute while it takes me 1.5 minutes. I am more powerful than you.
False
Energy of motion
What is kinetic energy?
Peter is setting a box down on the floor. Is positive or negative work being done?
negative work.
A unit of power which equals to one joule per second
The Watt?
Students do 75 Joules of work to push a table. How much energy was used by the students?
75 Joules
A 2.9 kg object has 656 J of kinetic energy. Calculate velocity.
21.3 m/s
A car is moving with a velocity of 20 m/s. The driver slams on the brakes when he/she sees a squirrel. What type of work is being done on the car? (positive or negative)
negative