Work
The applied force pushing a box is 100N. The box travels 43 meters. What is the work done by the applied force?
W = Fd = 100*43 = 4300J
A 0.62 kg basketball is 4m above the ground. g = 9.8m/s2. What is its potential energy?
PE = mgh
0.62(9.8)(4) = 24.3 J
It takes a marble 0.64 seconds to roll 1m. What is its velocity?
v = d/t = 1/0.64= 1.56 m/s
80N of force is pulling a cup down, while 70N of force is pushing the cup up. What is the net force on the cup?
10N downwards or -10N (need to indicate direction)
At which fast food restaurant can I get a Whopper?
Burger King
As a basketball falls 3m to the ground, air resistance pushes up with a force of 0.5N. What is the work done by air resistance to the ball?
W = -0.5*3m = -1.5J
A 5000kg elephant is running at 6m/s. What is her KE? KE = 1/2mv2
1/2*5000*6^2 = 90,000J
What's the difference between distance and displacement?
Distance is scalar. Is total length of the path traveled.
Displacement is vector. Is the overall change in position (shortest distance from start to end)
A marble is rolling on a flat table. Draw out the FBD. Make sure the arrows are labeled and the length of the arrows are proportional to their magnitude
Fg, N, fric, (shouldn't have a Fapp)
What was the mass (in kg) of the marble we used for our roller coasters?
~0.005 kg
If a car is traveling to the left and I want to slow it down, would I want to apply positive or negative work?
Tell me why that's the case.
Negative. Even though the direction of the force would be to the right, we consider it negative because is opposing the current motion / displacement.
A 54kg skater starts on a ramp that is 5m high. What is his initial potential energy (PE1)?
PE = mgh
54*9.8*5 = 2646J
Convert 0.70m to inches
1m = 100cm, 2.54cm = 1 in
(0.7 m / in) (100cm / m) (1 in / 2.54cm) = 27.56 inches
A car is slowing down at a rate of -2m/s2. The car’s initial velocity is 13m/s. What is the car’s final velocity 4 seconds later?
vf = vi + at
vf = vi + at
= 13 + (-2)(4) = 5m/s
Why is Black Friday called Black Friday?
Because "black" means profit, and the stores were supposed to make profit that day
A coffee mug is resting on the table. Its mass is 1.5kg. g = 9.8m/s2. Its sitting 2m above the ground. What is the work that gravity is doing to the mug?
PE = mgh
0J, the mug is not moving
A 54kg skater, at the bottom of a ramp, is traveling 4m/s. What is his final kinetic energy (KE2)?
1/2*54*4^2 = 432 J
Convert 65 miles per hour to m/s
1609 m = 1 mile & 3600 s = 1 hr
65 mi / hr * (1609 m / 1 mi) * (1 hr / 3600)
= 29 m/s
If the force of gravity on a ball is 40.9N, and the acceleration of gravity is 9.8/s2, what is the mass of the ball?
F = ma... m = F/a
m = 40.9 / 9.8 = 4.17kg
When is the winter solstice? (least amount of daylight)
Dec 21
Mr Incredible is slowing down a train. He pushes with a force of 40,000N to slow it down. He slows it over a distance of 150m. What is the work that Mr. Incredible does to the train?
W = F*d
40,000N * 150m = -6,000,000J
What is the energy lost to friction, if the initial PE is 2646J and the final KE is 432J, when a skater rides down a ramp?
2646-432 = 2214 J
What are the names of Santa's 3 reindeers that start with a D?
Dasher, Dancer, Donner
(Prancer, Vixen, Comet, Cupid, Blitzen, Rudolph)