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Physics - P5
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Gravity
Terms in this set (77)
What are five examples of vector quantities?
force, velocity, displacement, acceleration, momentum
What type of quantity is force?
Vector
What do vector quantities have?
a magnitude and a direction
What do scalar quantities have?
ONLY a magnitude and no direction
What are five examples of scalar quantities?
speed, distance, mass, temperature, time
what are vectors usually represented by?
an arrow
Length is what?
Magnitude
The direction is what?
The direction of the quantity
What is a force?
A PUSH or PULL on an object that is caused by interaction with something
What are ALL forces?
contact or non contact
What is a contact force?
when 2 objects must be touching for a force to act
What is a non-contact force?
when objects do not need to be touching for a force to act
What are five examples of contact forces?
friction, air resistance/drag, tension(in roped), normal contact force, upthrust
What are three examples of non-contact forces?
Magnetic, gravitational and electrostatic force
When two objects interact, where is a force produced?
on BOTH objects
What is an interaction pair?
pair of forces that are equal, opposite and act on two interacting objects
What is the definition of gravity?
The force of attraction between all masses
What is the force of gravity close to Earth due to?
Gravitational field around the planet
What is the definition of weight?
Force acting on an object DUE to gravity
What is the mass of an object related to?
The amount of matter it contains and its constant
What does weight depend on?
Gravitational field strength where the object is
What is weight directly proportional to?
Mass
What does gravity give a weight?
EVERYTHING
On the surface of a planet, where does gravity make everything fall towards?
The ground
What varies with location?
Gravitational field strength
Is gravitational field strength stronger or weaker the closer you are to the mass?
stronger
What is the symbol equation for weight?
W = mg
What is the word equation for Weight?
Weight = mass x gravitational field strength
What is the unit for weight?
Newtons (N)
What is the unit for mass in the weight equation?
kilograms (Kg)
What is the unit for gravitational field strength?
Newtons per kilogram (N/Kg)
What is the symbol equation for gravitational field strength?
g = W / m
Where does weight act from?
a single point on an object - centre of mass.
If there is a uniform object, where is the centre of mass?
at the centre of the object itself
Is mass a force?
No
If you increase the mass of an object, what will happen to its weight?
It will increase at an identical rate because they are directly proportional
If there are equal masses, what will the distances be like to the centre of gravity?
equal
If there are unequal masses, what will the distances be like to the centre of gravity?
unequal
What is a resultant force?
When more than one force acts on an object and these forces are seen as a single force that has the same effect.
In most real situations, how many forces are acting on an object along any direction?
at least two
If you have a number of forces acting at a single point, what can you replace them with?
a single force that has the same effect as all original forces together
How is overall effect found with forces going in the same direction?
Adding them together
How is overall effect found with forces that are going in the opposite direction?
Subtracting any going in the opposite direction
When a force moves an object through a distance, what happens?
Energy is transferred and work is done on the object
How do you make something move?
By applying a force
What does the thing applying force need?
A source of energy
e.g. food / fuel
The force does what to move the object?
work
Where is energy transferred from and to when work is done to move the object?
energy is transferred FROM one store TO another
How is energy transferred (two ways)?
'usefully' and 'wasted'
What symbol equation can you use to find out HOW MUCH work has been done?
W = Fs
What is the unit for work done?
Joules (J)
What is the unit for force?
Newtons (N)
What is the unit for distance moved along the line of action of force?
Metres (m)
What are the outcomes when you push something along a rough surface?
object moves (kinetic energy store), overall temp. of object increases (thermal energy store)
What type of drawing can you use to calculate forces?
Scale drawing
How do you draw forces using a scale drawing?
to SCALE - accurately!
What do the forces have to combine to give, if the object is in equilibrium?
a resultant force of 0
What can forces be split into?
Two componens at right angles
How can you resolve a force?
Drawing it on a scale grid
To change he shape of an object what must be applied?
More than one force
If an object does not return to its original shape after forces are removed, what is it?
Elastically deformed
If an object does not return to its original shape, what is it?
Inelastically deformed
What is the extension of an elastic object directly proportional to?
Applied force
What happens when the limit of proportionality has been exceeded?
Doubling force will no longer exactly double extension and relationship becomes non-linear
What's the equation linking force, spring constant and extension?
Force = Spring Constant x Extension
F = ke
What does the F = ke equation apply to?
linear section of a force-extension graph & compression of an elastic object
What does the spring constant indicate?
How easy it is to stretch/compress a spring
The higher the constant...
The stiffer the spring
What is work done equal to?
Energy stored.
A force that stretches or compresses a spring stores what type of energy in the spring?
elastic potential energy
What is a moment?
The TURNING EFFECT when a force causes an object to rotate about a pivot point
What is the equation that links distance, moment and force?
Moment = Force x Distance
M = fd
What is the equation for moment?
Moment (Nm) = Force (N) x Distance (m)
M = fd
If a force is balanced, what is equal to total clockwise moment around a pivot?
Total anticlockwise moment around a pivot.
What are the two uses for levers and gears?
-Transmit rotational effects of forces
-Enlarge either the size of applied force or the distance the force moves over.
What happens to force when the applied force moves further than transmitted force?
Force INCREASES
What happens to distance when the applied force is bigger than transmitted force?
Distance is INCREASED
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