# physics 3

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Examples of Scalars
distance, area, volume, speed, time, mass, energy, power, temperature, electric potential
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Examples of Vectors
displacement, velocity, acceleration, force, momentum, electric field strength, magnetic field strength
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Adding vectors to find the resultant vector
Vectors which act in the same direction or whose directions are exactly opposite to each other are easy to add together but you must take account of their directions.
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Adding vectors to find the resultant vector
Example 1. Two 5N forces acting to the right add together to give a 10N force acting to the right.
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Adding vectors to find the resultant vector
Example 2. A 10N force acting to the right and a 5N force acting to the left add together to give a 5N force to the right.
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Adding vectors which act at 90o to each other
We can use Pythagoras’ theorem and trigonometry to find the resultant of the vectors and the direction it is acting in. Two forces of 41N and 60N act at 90o to each other
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Moments
The moment (or torque) of a force about a turning point is the force multiplied by the perpendicular distance to the force from the turning point. Moments are measured in newton metres (Nm). Moment = F d
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The principle of moments.
” When an object is in equilibrium the sum of the anticlockwise moments about a turning point must be equal to the sum of the clockwise moments.” sum of anticlockwise moments = sum clockwise moments
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Couples
A couple is two equal forces which act in opposite directs on an object but not through the same point so they produce a turning effect. The moment (or torque) of a couple is calculated by multiplying the size of one of the force (F) by the perpendi
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Centre of Mass
The centre of mass of an object is the point at which all the mass of the object seems to act. In a uniform gravitational field this is the same point as the centre of gravity of the object which is where all the weight of the object seems to act.
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1) Newton’s first law
An object continues in a state of rest or uniform motion in a straight line unless acted on by a resultant force.
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2) Newton’s second law
The rate of change of momentum of an object is directly proportional to the resultant force applied and is in the direction of the resultant force. F=ma
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3) Newtons third law
When two objects interact they exert equal and opposite forces on each other.
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Momentum
he momentum (p) of an object is found by multiplying the objects mass (m) in kilograms (kg) by it’s velocity in metres per second (ms-1).
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momentum
Momentum is a vector and it’s unit is the kilogram metre per second (kgms-1).
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Newton’s Second Law
The rate of change of momentum of an object is directly proportional to the resultant force applied and is in the direction of the resultant force. The resultant force is equal to the rate of change of momentum.
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Impulse
If we multiply the force acting on an object by the time it is acting for this is called the impulse of a force. Impulse is a vector and its unit is the kilogram metre per second (kgms-1) or the newton second (Ns).
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Conservation of momentum
The principle of conservation of momentum when two objects interact the total momentum remains the same provided no external forces are acting.
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## Other cards in this set

### Card 2

#### Front

Examples of Vectors

#### Back

displacement, velocity, acceleration, force, momentum, electric field strength, magnetic field strength

### Card 3

#### Front

Adding vectors to find the resultant vector

### Card 4

#### Front

Adding vectors to find the resultant vector

### Card 5

#### Front

Adding vectors to find the resultant vector