Physics P5 (Forces part 1)

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What is a scalar quantity (with 3 examples)?
They have magnitutes (sizes) only such as speed ,time and mass
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What is a vector quantity (with 3 examples)?
They have magntitutes and a direction such as velocity, acceleration and force
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What are the 2 forces that forces between objects are under?
contact and non-contact
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What are 3 examples of types of contact forces?
friction, air resistance and tension
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What are 3 examples of types of non-contact forces?
gravitational, electrostatic, magnetic
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What is weight?
The force acting on an object due to gravity
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What is the force of gravity close to the Earth is due to?
the graviational field around the earth
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What does the weight of the object depend on?
The gravitational field strength at the point where the object is.
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How can weight be calculated?
mass x gravitational field strength
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What are the units for gravitational field strength?
N/kg
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What is an object's centre of mass?
the single point where the weight of an object is acting on
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What is the relationship between an object's mass and weight?
They are directly proportional
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How is weight measured?
By a calibrated spring-balance (newtonmeter)
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What is the single force that has the same effect as all the original forces acting together?
The resultant force
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How is work done on a object? (think of equation)
By when a force causes the object to move through a distance
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How can we calculate work done?
force x distance
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What is the unit of measurement for work done?
joules
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What does work done against a frictional force on an object cause?
a rise in temperature of the object
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What could cause an object to rotate?
A force or a system of forces
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What is the moment of a force also known as?
The turning effect of a force
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How can the size of the moment be calculated?
force x distance
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What does the distance have to be in terms of an angle?
perpendicular (90 degrees) from the pivot to the line of action of the force
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What can we say about the total clockwise and anticlockwise moment about that pivot if the object is balanced?
They are equal
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What can be used to transmit the rotational effects of forces?
A simple lever and a simple gear system
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What happens to the size of a force if the lever is longer for the effort is further away from the pivot?
It becomes greater
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What is applied to rotate one end of the pivot?
An effort
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Would a low gear on a bike have a higher or lower moment?
Higher
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Would a high gear on a bike have a higher or lower moment?
Lower
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Are the forces acting on both gears different or the same?
The same
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What two states of matter could a fluid be?
Liquid or gas
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What does the pressure in a fluid cause?
A force normal (at right angles) to any surface
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How can we calculate pressure?
Force normal to a surface/ area of that surface
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What is the unit of measurement of pressure?
pascals (Pa)
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How can we calculate the pressure due to a column of liquid?
height of column x density of liquid x gravitational field strength
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What is the unit of measurement of density?
kg/m^3
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Why does the pressure increase in liquids as the depth/density increases?
The pressure in a liquid is due to the weight of the column of water above. Since the particles in a liquid are tightly packed, this pressure acts in all directions.
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How does an object experience the upwards force (upthrust) in water?
When a partially (or totally) submerged object experiences a greater pressure on the bottom surface than on the top surface
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If there is a greater weight than upthrust, will the object float or sink?
Sink
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If there is a greater upthrust than weight, will the object float or sink?
Float
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How does increasing altitude affect the atmosphere's density?
It becomes less dense
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What creates atmospheric pressure?
Air molecules colliding with a surface
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Why does atmospheric pressure decreases with an increase in height?
The number of air molecules/ weight of air above a surface decreases meaning there is always less air above ground level compared with a lower height
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What is distance?
How far an object moves
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What type of quantity is distance and why?
It is a scalar as it does not involve direction
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What type of quantity is displacement and why?
It is a vector as it includes both the distance and the direction of a straight line
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What type of quantity is speed and why?
It is a scalar as it does not involve direction
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What are factors that can affected someone's speed to walk, run or cycle?
age, terrain, fitness, distance travelled already
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What is the typical speed of walking?
1.5m/s
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What is the typical speed of running?
3m/s
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What is the typical speed of cycling?
6m/s
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Does the speed of sound and wind also vary?
yes
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What is the typical value for the speed of sound in air?
330m/s
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How can speed be calculated?
distance travelled/ time
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What is velocity?
An object's speed in a given direction
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Is velocity a scalar or vector quantity?
Vector
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What can the speed of an object be calculated from in a distance-time graph?
the gradient
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what are the forces involved in stretching, bending or compressing an object?
weight (downwards) and tension (upwards)
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can elastic deformation be reversed and if so how?
removing the force that has been applied to the spring
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can inelastic deformation be reversed and if so how?
it can't as it has permanently changed shape
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what can be said about the extension and force of an elastic object?
They are directly proportional
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providing what?
that the limit of proportionality is not exceeded
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define limit of proportionality (think graph)
the point beyond where Hooke's law no longer applies,where the graph of force against extension starts to curve
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Using this graph, how can you calculate spring constant?
gradient (F/e)
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How do you work out elastic potential energy?
1/2 x k x e^2
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How do you work out the force applied to a spring?
k x e
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What is the unit for spring constant?
N/m
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What does a force that stretches or compresses a spring do (in terms of energy)?
work
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What type of energy is stored in the spring?
elastic potential
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if the spring isn't elastically deformed, what can be said about the work done on a spring and the elastic potential energy stored?
they are equal
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Other cards in this set

Card 2

Front

What is a vector quantity (with 3 examples)?

Back

They have magntitutes and a direction such as velocity, acceleration and force

Card 3

Front

What are the 2 forces that forces between objects are under?

Back

Preview of the front of card 3

Card 4

Front

What are 3 examples of types of contact forces?

Back

Preview of the front of card 4

Card 5

Front

What are 3 examples of types of non-contact forces?

Back

Preview of the front of card 5
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