Vocab
The product of force, displacement, and the cosine of the angle between them.
Work
What does work require?
Force, displacement, and that they are parallel.
A 7 kg object is motionless. Calculate kinetic energy.
A person walking their dog pulls on their leash with a force of 12 N for 5 m. What is the work done on the dog?
60 J
What is the law that states that energy cannot be created or destroyed but can be changed from one form to another
The law of conservation of energy.
The energy stored in a stretched or compressed object.
Work is positive when...
The force and displacement are in the same direction.
What is the formula for Kinetic Energy?
KE=1/2 m v^2
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.
What is the potential energy of a 4kg orange cat on top of a 3 meter high bookshelf?
GPE= (4kg)(10m/s^2)(3m)
GPE=120J
Energy of motion
Kinetic Energy
Is work a vector or scalar quantity? Why?
A scalar quantity because it has no direction, only a magnitude.
Name for energy that comes from heat
What is thermal energy?
A 5 kg rock is raised 30 m above the ground level. How much work is done to lift it?
W= 1500 Joules
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
The rate at which work is done.
Power
Energy - Work Theorem states that the work done an object equals the change in its ________
Kinetic Energy
How does potential energy differ from kinetic energy?
Potential energy is energy stored while kinetic is energy of motion.
Calculate the work done by a 47 N force pushing a pencil 0.26m
12 J
Steph is carrying her book across the room by balancing the book steady on her hand. Is work being done? Why or why not?
No, the force and displacement are not parallel.
A unit of power which equals to one joule per second
Watts
A 2.9 kg object has 656 J of kinetic energy. Calculate velocity.
21.3 m/s
A 60 W light bulb runs for 5 secs. How much energy does it use?
300 J
A 2,500 kg race car accelerates from rest to 35 m/s in 7.3 s. What is the power output of the engine?
209,763 W