Energy Transfer
Can Mechanical Energy ever change?
Why or why not?
Always constant , unless some energy is "lost" as heat
If Jon wants to use 5x10² N to push his little sister out of the 3m bed in 2 seconds, how much power must he produce to be successful?
750 Watts
If Timmy pushes the cart with 6N across a 30m parking lot, how much work can he do?
180 Joules
What are the formulas for GPE, KE, & ME?
PE = mgh
KE =(0.5)(m)(v2)
ME (w/o) = GPE + KE
ME (w/) = GPE + KE + Heat
What are the two formulas you can use to solve for Work?
W = F x d
W = KE2 - KE1
What happens to energy between the Top of a hill and the Bottom of a hill?
If I roll down the hill, then...
If I walk up the hill, then...
Energy transforms from one form to another
PE --> KE
KE --> PE
How much power can Jacky produce if she uses 15 seconds to do 178 J of work?
11.9 Watts
What are the missing formulas?
_______ = Work
_______ = Force
_______ = Distance
Force x Distance = Work
Work / Distance = Force
Work / Force = Distance
What is the GPE of a 40 kg lion sitting atop a 65 m tree?
25,480 J
Potential and Kinetic Energy are directly proportional.
True or False?
False, inversely
When air resistance is present, what will also be present?
Heat/Thermal
If Cristina does 40J of work over 25m, how much force does she use?
1.6 Newtons
As a skydiver falls to the earth, their ____ energy is converted into ____.
Draw the graphs that support this.
Gravitational Potential energy is converted into Kinetic energy.
This theorem states that energy can never be created or destroyed.
True or False?
False
If you fall from the top of a tower, and your velocity is measured at 3m above the ground, will your GPE(top) and KE(bottom) be equal?
Why or Why not?
No, because you haven't reached the ground (0m)
If Sheena uses 6x10²N to push her daughter in the swing, her daughter will fly 3 ft into the air in appx. 2.54 seconds. How much power must Sheena produce in order to accomplish this feat?
708.7 W
Hans Full is pulling on a rope to drag his backpack to school across the ice. He pulls upwards and rightwards with a force of 22.9 Newtons at an angle of 35 degrees above the horizontal to drag his backpack a horizontal distance of 129 meters to the right. Determine the work done upon the backpack.
2,954.1 J
A 35kg bowling ball is dropped from a height of 150m. By the time the ball reaches 10m above the ground, it has a velocity of 15 m/s. Calculate the GPE at the top and the KE at the bottom of the building if there IS friction.
**Hint = the GPE at the bottom IS NOT 0
Top : GPE = 51,450 J
Bottom : KE = 3,937.5 J
I've been pushing my 5 kg cart around the store at 19 m/s, but I'm tired. How much less work should I do to slow down to 10 m/s?
-652.5 J
A 25 kg medicine ball is dropped from a 30 m tower. Just before it hits the ground, it is traveling at 15 m/s. Was there any mechanical energy lost?
If so, how much and what happened to it?
Yes there was.
4, 537.5 J were lost as Heat.
A 1500 kg Honda is accelerating at 175 m/s² down a lonely, dark, 150 m back road. It crashes into a brick building 12 seconds later. How much power did the car produce?
3,281,250 Watts
During the Powerhouse lab, Jerome runs up the stairs, elevating his 102 kg body a vertical distance of 2.29 meters while accelerating at 10 m/s². How much work does he do?
2,335.8 J
A 35kg bowling ball is dropped from a height of 150m. By the time the ball reaches 10m above the ground, it has a velocity of 15 m/s. How much energy is "lost" as heat?
GPE (top) - KE (bottom) = Heat
47,512.5 J were lost as heat
What does the work-energy theorem state?
WORK DONE = ENERGY GAINED
OR
When work is done, energy is transferred from one form to another