Forces (5) - Pt3 Flashcards

1
Q

What’s the speed of a:

  • car
  • train
  • plane
A
  • car: 25m/s
  • train: 55m/s
  • plane 259m/s
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2
Q

What’s the speed of sound. And what can effect its speed?

A

330m/s in air

It can change depending on what the sound waves are travel traveling through

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3
Q

What effects the speed of a person?

A
  • fitness and age

- terrain they’re on

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4
Q

What can effect the speed of wind?

A
  • temperature
  • atmospheric pressure
  • large structures (eg. Forests reduce the speed of the air traveling through them)
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5
Q

What’s acceleration?

A

The change in velocity in a certain amount of time

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6
Q

How would you calculate the average acceleration of an object?

A

Acceleration (m/s*2) = change in velocity (m/s) / time (s)

a= change in v/ t

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7
Q

What’s deceleration?

A

Negative acceleration (the change in velocity is negative)

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8
Q

What’s uniform acceleration?

A

Constant acceleration

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9
Q

What’s the equation the links velocity, acceleration and distance?

A
Final velocity (m/s)*2 - initial velocity (m/s)*2 = 2 x acceleration (m/s*2) x distance (m)
V*2-u*2 = 2as
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10
Q

What does the gradient of a distance-time graph mean?

A

Speed

The steeper the graph the faster it’s going

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11
Q

What does a flat section on a distance-time graph mean?

A

Where it’s stationary

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12
Q

What do the straight uphill section on a distance-time graph mean?

A

It’s traveling at a steady speed

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13
Q

What does a curve on a distance-time graph mean?

A

Acceleration (a steeping curve means it’s speeding up) or deceleration (a levelling of curve means it’s slowing down)
(Draw a tangent to a point of the curve if you want to find the speed)

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14
Q

What does the gradient of a velocity-time graph mean?

A

The gradient=acceleration

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15
Q

What does a flat section on a velocity-time graph mean?

A

Represent traveling at a steady speed

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16
Q

What does the steepness of a velocity-time graph mean?

A
  • the steeper the graph the greater the acceleration or deceleration
  • uphill sections are constant acceleration
  • downhill sections are constant deceleration
17
Q

What does a curve on a velocity-time graph mean?

A

Changing acceleration

18
Q

What does the area under a a velocity-time graph mean?

A

The distance travelled

19
Q

If an object has no force propelling it along what will happen?

A
  • It will always slow down and stop because of friction
  • Friction always acts in the opposite direction to movement
  • To be at a steady speed the driving force need to equal the fictional forces
20
Q

When do you get friction?

A
  • between 2 surfaces in contact

- when an object passes through a fluid (drag)

21
Q

What’s drag? And give an example of a type of drag?

A
  • it’s the resistance you get in a fluid (a gas or liquid)
  • eg. Air resistance
  • drag increase as speed increses
22
Q

How can you reduce drag?

A
  • By keeping the shape streamlined

- this allows the fluid to flow easily across it

23
Q

Explain how object’s falling through fluids reach a terminal?

A
  • at the start the force of gravity is a lot more than the frictional Force, so it accelerates
  • as the speed increases friction builds up reducing the acceleration
  • until the frictional forces are equal to the accelerating force (so the resultant force is 0)
  • it will have reached terminal velocity and will fall at a steady speed
24
Q

What 2 things affect terminal velocity?

A

Shape and area

25
Using the example of a skydiver explain how the frictional force depends on the shape and area?
- without the parachute open he has a small area. He reaches a very fast terminal velocity - but with the parachute open there’s a lot more area resistance. So he has a lot slower terminal velocity
26
What’s Newton’s first law of motion?
- If the resultant force on a stationary object is 0, the object will remain stationary. - If the resultant force on a moving object is 0, it’ll just carry on moving at the same velocity
27
If the resultant force isn’t 0 what happens?
Acceleration (or deceleration) in the direction of the force
28
What different ways could they refer to “acceleration” (or deceleration) as?
1. Starting 2. Stopping 3. Speeding up 4. Slowing down 5. Changing directions 6. (On a free body diagram the arrows will be unequal)
29
What’s the relationship between resultant force and acceleration?
They’re directly proportional
30
What’s the relationship Between acceleration and mass (for a fixed resultant force)?
Acceleration is inversely proportional to mass