Science Study Guide Flashcards
Machines decrease the amount of energy that is needed to do work
True, cause apply less force
Because of friction, using machines increase the amount of energy needed to do work
True, cause of friction
An arrangement of multiple pulleys cause the direction of the output force to be opposite to the direction of the input force.
True, cause input force is opposite of output force
A first class lever can have a input force greater than the output force
When you lift on handle, you don’t need a lot of work
If a person tries to lift a heavy box for 5 seconds and can’t make it budge, the work done on the box is less than zero
False, cause it equals zero
A second class lever always has an input force that is less than the output force
True, when you lift on the handle you don’t need a lot of force
Increasing the angle a ramp makes with the horizontal decreases the mechanical advantage
True, mechanical advantage is equal to length divided by height
A meteorologist trying to predict global warming would consider earth to be a closed system.
False, open because there is an exchange of energy and matter
A ball falling under the force of gravity is a closed system.
True, no matter is exchanged
Increasing the length of a ramp increases the efficiency of the ramp.
True, longer the ramp, less force needed.
A quantity that measures the rate at which work is done is called what?
Joules
A quantity that measures how much a machine multiplies force or distance is called what?
Work
Power is calculated by dividing work by what?
Time
Horsepower is the common unit of power in rating engines. However, the official SI unit of power is the what?
Watt
All lovers have a rigid arm that turns around a point called the
Fulcrum
A —— is defined as a machine made up of more than one simple machine.
Compound machine
A —— is an inclined plane wrapped around a cylinder.
Screw
The ability to do work defines ——
Energy
The formula for calculating kinetic Energy can be written as ——-
KE= 1/2 • m • v 2
The stored energy resulting from the relative positions of objects in the system is called ——
Potential energy
The energy of a moving object due to its motion is called ——
Kinetic energy
The sum of the kinetic energy and potential energy of large-scale objects in a system is called ——-
Mechanical energy
Energy that lies at the level of atoms and does not affect motion on a large scale is sometimes called ——
Non-mechanical energy
The source of the energy when dynamite explodes is ——-
Chemical energy
The process that transforms light energy into chemical energy in plants is called ——-
Photosynthesis
The source of the energy is —–
Nuclear fusion
When a system exchanges energy with the environment outside the system, it is called a ——-
Open system
A ——- exchanges energy with the outside.
Closed
The ratio of useful work output to work input is a measure of ——-
Mechanical advantage
Energy is transferred as ——- when mechanical energy decreases and temperature increases
Friction
Three children exhaust himself trying to push a large rock that doesn’t budge. Have they done any work? Why?
No, because the object must move
Do machines reduce the amount of work we have to do? If not, why are machines so useful?
No, they only reduce the amount of input force needed to do the job.
How does a pendulum show the relationship between gravitational potential energy and kinetic energy?
Because of the gravitational pull on the objects a pendulum swings down then the acceleration brings it up then potential energy brings it back down.
What is nuclear fusion?
A kind of reaction in which right atomic nuclear combine to form a heavier nucleus
Why is light considered a form of energy?
Because light travels across empty space in the form of electromagnetic waves
What is the law of conservation of energy?
Energy cannot be created or destroyed, only transferred.
What is the difference between an open system and a closed system?
In the open system matter and energy are exchanged. In the closed system if energy is exchanged, matter is not
What is meant by the efficiency of a machine?
The efficiency of the machine is a measure of how much useful work a machine can do. Efficiency equals useful work output divided by work input.
Where does energy go when it seems to disappear?
It does not disappear, just changes form
