7K Forces Flashcards

1
Q

What things could a force do to an object?

A

Forces can make things:

  • Speed up
  • Slow down
  • Change direction
  • Change shape
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2
Q

Do forces have just size, just direction, or size and direction?

A

Forces have size and direction.

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3
Q

On a diagram, what can we use to show a force?

A

On a diagram you can use an arrow to show a force.

The length of the arrow shows the size of the force, and the direction the arrow is pointing shows the direction the force will act.

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4
Q

What is meant by a contact force?

A

A contact force is one in which objects are touching. For example, kicking a ball, or friction.

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5
Q

What is meant by a non-contact force?

A

A non-contact force is one where the objects are not touching. For example, magnetism and gravity.

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6
Q

What is friction?

A

Friction is a force that slows things down. It always opposes movement.

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7
Q

What can you use to reduce friction?

A

To reduce friction, you can use lubrication. for example, oil on a bike chain.

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8
Q

What is meant by balanced forces?

A

Balanced forces are forces which cancel each other out, so there is no change in movement.

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9
Q

What is the name of the force labelled X?

A

The force labelled X is the weight.

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10
Q

What is the name of the force labelled Y?

A

The force labelled Y is drag or friction.

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11
Q

If the force from the engine is bigger than force Y, what happens to the boat?

A

If the force from the engine is bigger than force Y then the boat will speed up or accelerate.

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12
Q

What can you say about the size of force X compared to the upthrust?

A

The forces are balanced, so force X (the weight) must be equal to the upthrust.

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13
Q

What is meant by pressure?

A

Pressure is a measurement of how spread out a force is.

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14
Q

Explain, using ideas about pressure, why wading birds have webbed feet.

A

Wading birds have webbed feet because they need to walk on mud without sinking. The webbed feet have a large area meaning the force is spread out and the pressure is less. This stops them sinking in.

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15
Q

What units is pressure measure in?

A

Pressure is measured in Pascals or Newtons per metre squared.

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16
Q

Calculate the pressure when a boy of weight of 400 N sits on a chair with an area of 0.25 m2.

A

Use the formula:

Pressure = force / area

= 400 / 0.25

= 1600 N/m2

17
Q

What causes air resistance?

A

Air resistance is caused by friction between the air particles and the moving object.

18
Q

What happens to air resistance if you are travelling faster?

A

If you are travelling faster, air resistance increases.

19
Q

Why do mountain bikes have wide tyres?

A

Mountain bikes have wide tyres:

  1. to increase friction (and stop you sliding around)
  2. to decrease the pressure (spread the force over a large area so that you don’t sink in to the mud)
20
Q

What is the formula to calculate pressure?

A