Vocabulary
the ability to do work
What is energy?
Equation for Work.
What is Work = Force x distance?
Replacing LED bulbs with incandescent bulbs will not conserve energy. (True/False)
What is false.
The energy contained in a moving object
What is kinetic energy?
The attraction of molecules and the interlocking of surface irregularities create ______.
What is friction?
The amount of work done or energy provided in a period of time.
What is power?
A force was used to push a box along the floor for a distance of 8 m. If 160 J of work was done, what force was applied?
d = 8 m W = 1400 J
W = Fd F =W/d
F = (1400 J)/(8m) = 175 N
What is nonrenewable?
The stored energy in a stationary object
What is potential energy?
Calculate the mechanical advantage when the effort force is 64 N and the resistance force is 192 N?
MA = resistance force/effort force
MA = 192 N/ 64 N = 3
a device that makes work easier by changing the size or direction (or both) of a force
What is a machine?
How much work is done when lifting a 4.8 kg bucket 2.9 m?
W=Fd
d = 2.9 m m = 4.8 kg
F = ma = (4.8 kg)(9.8 m/s2) = 47.04 N
W = (47.04 N)(2.9 m) = 136.42 J
The force needed to do the same work with a machine.
What is effort force?
If an arrow has a mass of 0.04 kg and travels at a speed of 45 m/s, what is its kinetic energy?
KE = 1/2mv2
KE = 1/2(0.04 kg)(45 m/s)2
KE = 40.5 J
________mechanical advantage is a better representation of how a machine works than ____________mechanical advantage.
What is Actual, ideal?
The measure of energy transferred when a force is applied to an object that causes it to move, and at least part of the force is in the direction of the movement.
What is work?
The scientific definition of work states that force and motion must be _____ to each other.
What is parallel?
How much power does a crane develop doing 60,000 J of work in 5 minutes?
P = W/t
t = 5 min = (5x60)= 300 sec
P = 60,000 J / 300 sec = 200 W
State the law of conservation of energy.
What is energy can not be created nor destroyed?
If a machine has an IMA of 8 and an efficiency of 60%, what is the AMA? What does that mean?
AMA = IMA x efficiency
AMA = 8 x 0.6 = 4.8
The machine increases the effort force by a factor of 4.8.
A measure of the amount of useful work done by the machine compared with the amount of work done to make the machine operate.
What is efficiency?
How much power is needed to lift a 3 kg crate 5 m in 6 seconds?
F = ma = (3 kg)(9.8 m/s2) = 29.4 N
W = Fd = (29.4 N)(5 m) = 147 J
P = W/t = 147 J/6 s = 24.5 W
What is the mass of an object traveling 20 m/s with kinetic energy of 4000 J?
v = 20 m/s KE = 4000 J
2KE/v2 = m
m = 2(4000)/(20)2
m = 20 kg
If 2 boxes have an identical mass of 25 kg, and 1 falls 1.5 m and the other falls 0.4 m, which one has more potential energy? How much more?
PE = mgh
PE1 = (25 kg)(9.8 m/s2)(1.5m) = 367.5 J
PE2 = (25 kg)(9.8 m/s2)(0.4m) = 98 J
367.5 J - 98 J = 269.5 J (The first box has 269.5 J more potential energy.)
If the work output of a machine is 2400 J and the work input is 3200 J, what is the efficiency of the machine? Why is the output less than the input?
efficiency = 2400 J/ 3200 J x 100 = 75%
Some of the energy is converted into heat energy through friction.