Force And Work Flashcards

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1
Q

Measuring force

A

Unit : Newton (N)
Named after Sir Isaac Newton
1 N is approx the force needed to support an apple.
Measured using Newton-meter or Spring balance

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2
Q

Weight

A

The weight of an object is the force of gravity on it.
Pull of the earth is stronger at the poles.
Weight of an object on the moon is a sixth of what it is on earth.

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3
Q

Weight and mass

A

We mix up the two.
A weighing scales gives the mass of an object.
Mass is measured in kg.
Weight is a force and is measured in newtons.

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4
Q

Acceleration

A

Acceleration due to gravity is approx 10 m/s2

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5
Q

How to find weight (in newtons)

A

Multiply mass (in kg) by acceleration due to gravity (10 m/s2)

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6
Q

Force

A

A force is something that causes an object to accelerate

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7
Q

Friction

A

Friction is a force which opposes motion between two objects in contact.

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8
Q

Disadvantages of friction

A

Friction slows things (why ships travel slower than planes).
Friction results in waste of energy (food mixers and car engines produce a lot of unwanted sound and heat energy).
Friction wears away surfaces in contact with each other (tyres lose their thread and brake pads on bicycles wear away).

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9
Q

Advantages of friction

A

It slows things down (brakes in a car or bike).
Friction between the road and wheels allow the thing to move. It allows us to walk.
Friction allows us to write and pick things up.

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10
Q

Lubrication reduces friction

A

Oil and grease are lubricants.

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11
Q

Stretching forces

A

Said to be elastic.
When a force is put on them they change shape.
When the force is removed they return to the original shape

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12
Q

Hookes law

A

The extension of a spring is directly proportional to the force that is stretching it

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13
Q

Work

A

Work done = force x distance moved
Measured in joules. Distance moved is measured in metres.
E.g. swimming

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14
Q

Energy

A

Energy is the ability to do work.

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15
Q

Power

A
Measure of how quickly work is done. 
Energy used per second. 
Power is the work done per unit time. 
Power = work done/time taken
Measures in watts
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