Y9 forces
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Author:
AHutson
ID:
244293
Filename:
Y9 forces
Updated:
2013-11-01 06:48:10
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Y9 forces
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Description:
Y9 forces
Show Answers:
What is a moment?
The
turning effect
of a force
How are moments calculated?
Moment (Nm) = Force (N) x distance from pivot (m)
What is a pivot?
The point around which something turns
What is
fulcrum
an alternative word for?
Pivot
What is a
lever
?
Something that uses moments to make a task require less force (make it easier)
Name some examples of levers
Can opener
Scissors (especially nail scissors)
Wheel barrow
Crowbar
Wheel spanner
What do we know about the anti-clockwise moment and the clock wise moment if an object is not turning?
They are
balanced
What are the units for force?
Newtons (N)
What are the units of distance?
Metres (m)
What are the units of moments?
Newton metres (Nm)
What is a pendulum?
An object that swings to and fro
What affects the time that a pendulum takes to make a complete swing?
The length of the pendulum (nothing else!)
What name we give to the time for a pendulum to make a complete swing (back to its starting place)?
Time Period
What unit is used to measure time?
second (s)
What unit is used to measure speed?
Metres per second (m/s)
What unit is used to measure acceleration?
Metres per second squared
What is the equation for calculating acceleration?
change in speed / time taken
Name the force that keeps objects moving in a circle
Centripetal force
In which direction does centripetal force act?
Towards the centre of the circle
What is the unit of centripetal
force
?
Newtons (N)
What
three
things affect the size of the centripetal force needed to keep an object moving in a circle?
Radius of the circle
Speed of the object
Mass of the object
Does increased speed need a larger or smaller centripetal force?
Larger
If the radius of the circle increases, what effect does this have on the centripetal force needed?
It reduces
If the mass of the object increases, what effect does this have on the centripetal force needed?
Increases
What provides the centripetal force that keeps the Earth orbiting around the Sun?
Gravity
What provides the centripetal force that keeps a conker tied to a piece of string moving in a circle
The
tension
in the string
In which direction does air resistance act?
Opposite to the direction of travel
If the speed of an object increases, how does this affect the air resistance?
Air resistance increases
If forces are balanced what do we know about the speed of an object?
It moves at a constant speed.
(If it was not moving it stays not moving)
What is terminal velocity?
The speed an object moves at when the forces acting on it are balanced.
eg a skydiver falling when her weight and air resistance are equal
Why does opening a parachute increase air resistance?
The parachute has a large surface area
What are the two units of
pressure
?
or Pascals (Pa)
What is the equation to calculate
pressure
?
What are the units for Area ?
What is
inertia
a measure of?
How hard to start or stop something moving
What
two
things affect the inertia of an object?
Mass
Speed
When a skydiver is falling, does her
weight
or
air resistance
change as her speed changes?
Air resistance (Her weight is constant)