# Physics-Forces

## Terms

undefined, object
copy deck
a force is nearly always . . .
a push or a pull
a force can cause change in . . .
speed, shape or direction

tof

forces acting on bodies act alone

false -hardly at all

the overall effect of the forces must be considered

if the forces acting on a body are equal and opposite, what will happen to speed and/or direction?

speed or direction won't change
any moving object has ____ acting against it
friction
if forces are balanced the object is doing one of two things. Go for it.
1. moving at a constant speed
2. stationary
resultant forces are also known as what?
unbalanced forces
a force is always stated as a ___ and a ____. Give the unit
as a size (N) and a direction

state

Newton's first law of motion

a body stays at rest or if moving continues to move at a constant velocity unless a resultant force acts on it

define, give units and state measuring apparatus for mass

mass is the amount of matter contained in a body, measured in kilograms (kg) by a scale or balance
define, give units and state measuring apparatus for weight
weight is the force putting a body towards the center of a planet due to gravity, measured in Newtons (N) by a Newtonmeter
give the equation for weight

weight = mass X acceleration due to gravity

w=m X g

Which of these changes if your on the moon (compared to earth)? How would it change?

2.  your weight would get lighter

NB. Your weight on the moon would be one sixth of what it is on earth.

work is only done when a force causes movement. What's the formula for work done?

work done = force X distanced moved in direction of force

w.d. = f X d

what's another way of saying 1Nm?

1 joule

NB. N X m = Nm/joule

5kg =__ N
50N
700g = __KJ
0.007KJ
work done is the same as saying . . .
. . .energy transfered
define and give the equation for power

power is the rate of doing work, measured in watts

power = work done/time taken

p = w.d./t

give all units for equation of power

power        = (kilo)Watts ((k)W)

work done  = joules

time taken = seconds (not minutes!)

1J per second is what? (clue in the last word, the question is the answer!)
1W

odd 1 out and reason why

sound, pressure, electricity, heat, light

pressure - the rest are energy forms

odd 1 out and reason why

oil, geothermal, solar, wind

oil - the rest are renewable
solar cells change ____ into ____
light into electricity
batteries store ______ energy
chemical
What's the equation for gravitational potential energy?

PE = mass X acceleration due to gravity X difference in height

PE = m X g X h

What's the equation for kinetic energy?

KE = 1/2 X mass X speed squared

KE = 1/2 X m X v2

What is all NRG measured in?
joules
What's the equation for efficiency?

efficiency = useful energy out/total energy in

eff = out/in = # between 0 and 1

All machines are less than 100% efficient. What form of energy does the waste usually take?
sound/heat
How is efficiency measured?
The efficiency of something is a number from 0 to 1, sometimes given as a percentage.

define

convection

the flow of heat through a liquid or a gas from places of higher temperature by movement of the liquid or gas particles themselves

define

conduction

the flow of heat through matter from places of higher temperature. The particles don't change position, they simply vibrate. Solids are the best conductors

define

the flow of heat from one place to another by electromagnetic waves not needing material to pass through
A dynamo changes ____ into ____.
KE into electricity
Energy cannot be created or destroyed . . .
. . . it can only be converted from one form into another.
A radio changes ___ into ___.
electricity into sound
An electric fire changes ___ into ___.
electricity into heat/light
An atomic bomb changes ___ into ___.
nuclear into heat/light/kinetic/sound
A burning candle converts ___ into ___.
chemical into light/heat
A jack-in-the-box converts ___ into ___.
strain PE into KE

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davidcampbell