Mixed Review
The rate at which work is being done is called ______.
power
Give the name for stored energy and give the formula used to calculate it.
potential energy
GPE = mgh
Energy due to the position of something and the movement of something is called _____.
mechanical energy
Give the formula and give the unit used to measure work.
W = Fd
Joules (J)
This multiplies your force or changes the direction of your force.
machine
The product of the net force on an object and the distance through which the object moved is called _____.
work
Give the name for the energy of motion and give the formula for calculating it.
kinetic energy
KE = 1/2mv2
True or False
Mechanical energy is the total amount of kinetic and potential energy in a system.
true
Give the formula and give the unit used to measure power.
P = W/t
Watts (W)
This is a simple machine made of a bar that turns about a fixed point.
lever
The property of an object or system that enables it to do work is called _____.
energy
You lift a 1.8 kg physics book 5 m off the floor. Calculate gravitational potential energy of the book.
GPE = (1.8 kg) (10 m/s2) (5 m) = 90 J
Calculate the total ME for a 50 kg skier moving at 2 m/s at the top of a 25 m hill.
KE = 1/2 (50 kg) (2 m/s)2 = 100 J
GPE = (50 kg) (10 m/s2) (25 m) = 12,500 J
ME = KE + GPE = 12,600 J
Doing the same work over a longer amount of time increases / decreases the power.
decreases
______ of a machine is the number of times the machine multiplies your effort.
mechanical advantage
Kinetic energy depends on ______ and _______.
mass and velocity
Calculate the kinetic energy of a 0.5 kg baseball moving at a speed of 105 m/s.
KE = 1/2 (0.5 kg) (105 m/s)2 = 2756 J
Calculate the total ME of a drone with a mass of 18 kg is flying with a velocity of 10 m/s at a altitude of 17 m.
KE = 1/2 (18 kg) (10 m/s)2 = 900 J
GPE = (18 kg) (10 m/s2) (17 m) = 3,060 J
ME = KE + GPE = 3,960 J
A 300 N force is required to push a wagon 20 m in 10 s. Calculate how much work in being done.
W= Fd
300 N x 20 m = 6,000 J
A kind of lever that can be used to change the direction of force.
pulley
Gravitational potential energy depends on _______ and ________.
weight and height
Energy cannot be created nor destroyed. However, it can escape a system in the form of _____.
heat energy
Calculate the total ME of a 2 kg remote control car that is moving at a velocity of 7 m/s at it approaches the edge of a cliff that is 1,800 m high.
KE = 1/2 (2 kg) (7 m/s)2 = 49 J
GPE = (2 kg) (10 m/s2) (1,800 m) = 36,000 J
ME = KE + GPE = 36,049 J
You lift a heavy box with a force of 75 N a distance of 2.3 m in 1.5 seconds. Calculate power.
P = Fd / t
(75 N) (2.3 m) / 1.5 sec = 115 W
Calculate the efficiency of a generator that has an output of 5,000 J and an input of 5,700 J when operating a full load.
= 88 %