Work, Energy, Power
In physics, work is defined mathematically as __________.
What is force times distance
A car has 100 J of energy. If you triples the car's velocity how much energy will it have?
What is 9x as much energy?
An object is dropped from a cliff, just before it hits the ground it has 60 J of energy, how much potential energy did the object have before it was dropped assuming no friction?
What is 60 J?
A net force of 56 Newtons is applied to a moving cart for 48 seconds. During this time the cart travels 22 meters. How much power was used to move the cart?
What is 25.67 W?
P = W/t
P = (Fxd)/t
P = (56 x 22)/48
How long is the shortest St. Paddy's Day Parade?
a. 26 ft
b. 98 yds
c. 98 ft
d. 26 yds
What is d?
Power is defined as ___________
What is work done on an object divided by the time taken to do the work
Where does a pendulum have the most kinetic energy?
What is at the bottom of its swing?
An object is dropped from a cliff, just before it hits the ground it has 60 J of energy, how much potential energy did the object have just before it was dropped assuming friction?
What is > 60 J?
How much farther will a car traveling at 40 m/s skid compared to the same car traveling at 10 m/s?
What is 16 x farther?
KE ~ (4v)^2
16 X
What city dyes its river green every St. Patrick's Day?
a. Manchester
b. Budapest
c. Amsterdam
d. Chicago
What is Chicago?
You run up a set of stairs, then you walk up the same set of stairs. In which case did you use the most energy? In which case did you use the most power?
What is
a. you used the same energy
b. more power when running
A 5 kg mass is lifted 7 meters from the ground. Calculate the change in potential energy.
What is 343 j?
A ball is thrown vertically upwards and then returns to the ground. If friction is present, how does the original energy that the ball had when thrown upwards compare to the final energy when it returns to the ground? What happened to the lost energy?
What is less and lost to heat and sound
Suppose a moving car has 2000 J of kinetic energy. If the car’s speed doubles, how much kinetic energy would it then have?
What is 8000 J?
KE ~ (V)^2
KE ~ (2V)^2
4 X 2000 = 8000 J
What was Saint Patrick's real name?
a. Seamus
b. Darragh
c. Maewyn
d. Aengus
What is c. maewyn?
Which requires more work: lifting a 50 kg sack vertically 2 meters or lifting a 25 kg sack vertically 4 meters?
What is both require the same amount of work?
A 55 kg runner is moving at a speed of 3 m/s, calculate the runners kinetic energy.
An 8 kg mass required 120 J of work to lift from the ground in 7 seconds. What is the height to which the mass was lifted and what is the power output?
a. 1.53 meters
W = mgh
W/mg = h
120/(8x9.8) = 1.53 m
b. 17.14 Watts
P = W/t
P = 120/7 =17.14 W
A 4.00-kilogram ball is dropped from the top of a building. Just before striking the ground, the ball’s kinetic energy is 30 J. What was the ball’s gravitational potential energy, relative to the ground, at the instant it was dropped?
What is 30 J?
Ei = Ef
Where was St. Patrick born?
a. Ireland
b. Germany
c. Britain
d. Norway
What is c. Britain?
You run up a set of stairs, then you walk up the same set of stairs. In which case did you use the most power?
What is running?
How much farther will a car traveling at 20 m/s skid compared to the same car traveling at 10 m/s?
What is 4x as far?
A child does 0.25 joules of work to compress the spring in a pop up toy. If the mass of the toy is 0.015 kg, what is the maximum vertical height that the toy can reach after the spring is released?
What is 1.7 m?
W = mgh
.25/(.015 x 9.8) = 1.7 m
An electric motor lifts a 7 N block a distance of 4 m. The total amount of electrical energy used by the motor is 40 J. How much energy was lost to heat?
What is 12 J?
Ei = Ef + w
40 = (7 x 4) + w
40 = 28 + w
40 - 28 = 12 J
According to Irish Lore, what did Saint Patrick drive out of Ireland?
a. witches
b. demons
c. rats
d. snakes
What is d. Snakes?