# Physics 8 and 9, Forces and Motion

What is a scalar and give some examples?
A quantity that has a size (magnitude) but no direction Examples: Speed, power, mass, volume, distance, time, energy
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What is a vector and give some examples?
A quantity that has both a size (magnitude) and a direction Example: Force, acceleration, momentum, weight, g.f.s
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What is displacement?
A distance in a particular direction
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Which forces are contact and which are non-contact?
Contact: Air-resistance, Spring, Tension, Frictional Non-Contact: Electrostatic, Magnetic, Gravitational
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What is a resultant force and what effect does it have an object?
-The resultant force is the overall effect of all the forces acting on an object -If the resultant force is 0, the object stays at constant velocity (same speed/stays still) -If the resultant force is greater than 0, the speed or direction changes
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Where is the Centre of Mass on a regular object, how would you define Centre of Mass?
Where its lines of symmetry cross, Centre of Mass is the point on an object where the mass is concentrated
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What is a parallelogram of forces and how is used to work out the resultant force?
It is a scale diagram of two force vectors. You then use a compass to create a parallelogram and measure the diagonal line, that is the resultant force, you must remember to apply the scale to it
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How do you work out distance travelled on a velocity time graph?
-You work out the area under the graph -Only works on a VELOCITY time graph
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How can two vehicles have the same speed but different velocities?
-Speed is the pace the object moves at e.g. 30m/s so two vehicles can both be moving at the pace -Velocity refers to the direction of the pace, one vehicle may be going north and the other on a roundabout so would have a constantly changing velocity
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What does the gradient of the line on a velocity-time graph represent
-It represents acceleration -If it is a positive gradient it represents a positive acceleration -If it is a negative gradient it represents a negative acceleration (deceleration) -If it is horizontal, there is no acceleration
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How do you work out the speed at any point on a curved distance-time graph?
-Draw a tangent at the point -Use this to create a triangle -Work out the gradient (change in y/change in x)
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What is a moment and how do you make a moment bigger?
-A moment is the turning effect of a force about a pivot -To make it bigger you can increase the force or increase the distance from the pivot
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What is the equation for the moment of a force?
Moment= force x distance, where distance is perpendicular from the line of action of the force to the pivot
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How do levers help to lift heavy objects?
-The weight of the object is the load -The force applied to the lever is the effort -The point about which the lever turns is the pivot -Using the lever, the effort needed to lift the object is a fraction of its weight -A lever is a force multiplier
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How does the force you apply to a lever affect how it moves the object?
-If you put in a small force, the lever must move a greater distance to get the same outcome (lots of little pushes) -If a apply a larger force, it must go a smaller distance to produce the same effect (one large push)
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## Other cards in this set

### Card 2

#### Front

What is a vector and give some examples?

#### Back

A quantity that has both a size (magnitude) and a direction Example: Force, acceleration, momentum, weight, g.f.s

### Card 3

#### Front

What is displacement?

#### Back ### Card 4

#### Front

Which forces are contact and which are non-contact?

#### Back ### Card 5

#### Front

What is a resultant force and what effect does it have an object?

#### Back 