Vocab
What does work require?
Force and displacement are parallel.
force acting upon an object and the object's movement to be in the same direction.
A 7 kg object is motionless. Calculate kinetic energy.
0 J
A 500 kg roller coaster is traveling 7 m/s at a height of 25 m. Calculate mechanical energy.
134750 J
this type of thermal energy transfer that causes a metal pan to heat up when it is placed on a stove.
conduction
The energy of motion is called ...
kinetic energy
True or False? Walking up stairs uses less force than running up stairs.
False. They are the same distance and same mass, so work would be the same.
True or False? Work is equal to a change in kinetic energy.
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.
Transfer of thermal energy when warm fluids rise, and cool fluids sink, creating a current.
convection
Stored energy is known as
What is potential energy?
True or False? Any part of a force that does not act parallel to the direction of motion does no work on an object.
True.
You are riding in a roller coaster going up a hill, at the top your car stops briefly before you start racing down to the bottom of the hill. At which point (stopped at the top or stopped at the bottom of the hill) do you have the most potential energy? Explain your answer..
stopped at top of hill because it has higher height (GPE = ham)
A 1kg ball is thrown upward and it stops at a height of 0.8 m. What is the ball's speed when it first left the thrower's hand? (g=10 m/s2)
4 m/s
This type of thermal energy transfer is why you feel warmth from the sun.
radiation
True or False? (Assume masses are equal.) You and me both move our books upstairs. You get up there in 1 minute while it takes me 1.5 minutes. I am more powerful than you.
False
You are riding in a roller coaster going up a hill, at the top your car stops briefly before you start racing down to the bottom of the hill. At which point (stopped at the top or racing towards the bottom of the hill) do you have the most kinetic energy? Explain your answer.
racing towards the bottom of the hill because you are moving
Choose the situation in which the person has the most power, then explain why.
Walking 2 miles
Running 2 miles
Crawling 2 miles
Running 2 miles because it takes less time
(P = w / t )
A unit of power which equals to one joule per second
The Watt?
If the force applied to an object that is moved is quadrupled but moved for half the original distance, what happens to the work done?
Twice the Work
A 2.9 kg object has 656 J of kinetic energy. Calculate velocity.
KE = (1/2)mv2
21.3 m/s
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?
Force is 200 N Formula : Power=work/power Time is 1.0 s = Force X Distance/ Time Distance is 1.5 m Power=200 N X 1.5 m/1.0 s = 300J/s= 300 W Formula: Power= work/time
When a car burns gasoline it creates hot air to move the pistons in the engine, which causes the car to move. What energy transformation occur from the fuel to the movement of a car?
chemical energy to thermal energy to mechanical energy