Machines
Work is done when a ______ is applied in the direction of motion.
What is force?
What does a mechanical advantage of 2 mean?
It takes 1/2 the force to move the object than would be required without the machine.
The total amount of this is the same before and after any transformation.
What is energy?
Heat flows from ____ objects to _____ objects.
What are warmer and cooler?
You throw a ball straight up into the air. Describe what happens to the Potential and Kinetic Energy of the ball as it is traveling.
You transfer chemical energy from your muscles into kinetic energy in the ball. The ball starts with 100% KE and 0% PE, slows down as it reaches the peak of the arc until it stops right at the top for a split second. At that time, it will have 100% PE and 0% KE. The ball then falls back down, as PE gradually converts to KE, until you catch the ball when it is at 100% KE and 0% PE. Then, the kinetic energy of the ball is transferred into your hand as thermal energy.
_____make it easier to do work.
What are machines?
What is the mechanical advantage of single pulley attached to a load, that can move?
MA = number of movable ropes.
Since the pulley can move, the number of movable ropes is 2. Therefore, MA = 2
The two basic types of energy.
What are kinetic and potential?
The measure of the average kinetic energy of the particles in an object.
What is temperature?
A diver with a mass of 50kg dives off of a 10m platform. What is his potential energy right before he dives? (Remember gravity = 9.81 m/s2)
PE = mgh = (50kg) x (9.81 m/s2) x (10m) = 4,905J
These three form the inclined plane family.
What are the inclined plane, the wedge, and the screw?
It would take 100Nm of work to move a box up 1m without a machine. You make a 4m long ramp to make the task easier. How much work do you need to do now?
Woutput = Winput /MA and MAramp = length/height
MA = 4m/1m = 4
Woutput = 100Nm/4 = 25 Nm
The total amount of energy in a system that is either doing work or resisting work.
What is mechanical energy?
Thermal energy is this.
What is the total energy of all the particles in an object?
A 1,350kg car is traveling at 12 m/s. What is its kinetic energy?
KE = 1/2 mv2 = 1/2 x (1,350kg) x (12m/s x 12m/s) = 97,200J
____ are classified according to the location of the fulcrum relative to the input and output forces.
What are levers?
What is the mechanical advantage of a lever with 6m between the input force and the fulcrum and 2m between the output force and the fulcrum?
MA = output distance/input distance
MA = 6/2 = 3
According to the law of conservation, this is true about energy.
That energy cannot be created or destroyed.
As the thermal energy of matter increases, its particles usually _____, causing the substance to _____.
What are spread out and expand?
MEtotal = PE + KE = 20J + 2J = 22J
The pulley and wheel & axle make use of what?
What is turning/rotating motion?
A truck (compound machine) has the following simple machines within it. Calculate the total mechanical advantage:
Wheel and Axle: MA = 5
Fixed Pulley: MA = 1
Block and Tackle Pulley: MA = 3
List 3 forms of energy associated with the particles of objects.
What are nuclear, thermal, electrical, electromagnetic, and chemical energy?
The three methods of heat transfer.
What are conduction, convection, and radiation?
There are two jars. Jar A has 100 g of water at 30 C. Jar B has 200 g of water at 30 C. Which Jar has more thermal energy?
Jar B. Since the temperature is the same, all the water molecules are moving at the same speed, but Jar B has twice as many molecules moving at that speed. Therefore, it has twice the amount of thermal energy as Jar A.