5. Forces Flashcards

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1
Q

To stretch, bend or compress an object,

A

more than one force has to be applied

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2
Q

Force

A

A push/pull exerted by one object onto another

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3
Q

Elastically deformed

A

Returns to og shape when force removed

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4
Q

Inelastically deformed

A

Won’t return to og shape when force removed

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5
Q

Principle of moments

A

For an object to be in rotational equilibrium (balanced), the sum of all clockwise moments must be equal to the sum of all anticlockwise moments

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6
Q

Lever

A

A tool that gives a mechanical advantage

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7
Q

Gear

A

Circular discs interlocking to transmit rotational motion.
The smaller the gear, the faster it rotates.
Varying the output force based on the ratio of the number of teeth.

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8
Q

If a fluid is heated, why does pressure increase?

A

Particles gain Eke
Particles collide with walls more frequently
Particles exert a greater force in each collision

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9
Q

How does a hydraulic system act as a force multiplier system?

A
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10
Q

Upthrust

A

When the pressure from below an object is larger than the pressure from above, the resultant force is upthrust.

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11
Q

Floating

A

Upthrust = Weight

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12
Q

Sinking

A

Upthrust < Weight

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13
Q

Density and upthrust

A

If the density of the object is lower than the fluid, then only part of it must be submerged for it to float.

Higher density - More submerged

If the density of the object is higher than the fluid, it will never displace enough fluid to equal weight

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14
Q

Acceleration

A

Increase V
Decrease V
Change direction

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15
Q

Newton’s First Law

A

If the resultant force on an object is 0, that object will continue to move at a constant velocity

Therefore: If an object experiences a resultant force, it will accelerate in the direction of the resultant force.

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16
Q

Inertia

A

The tendency of an object to remain at its’ current velocity

17
Q

Newton’s Second Law

A

The acceleration of an object:

  • Directly proportional to resultant force
  • Inversely proportional to inertial mass
18
Q

Newton’s Third Law

A

If body A exerts a force on Body B, then Body B will exert an EQUAL and OPPOSITE force of the same type.

19
Q

Walking

A

1.5m/s

20
Q

Running

A

3m/s

21
Q

Cycling

A

6m/s

22
Q

Car

A

25m/s

23
Q

Train

A

55m/s

24
Q

Plane

A

250m/s

25
Q

Sound

A

340 m/s

26
Q

Light

A

300 000 000 m/s

27
Q

Terminal velocity

A

initially air resistance is less than weight / gravity

so the skydiver accelerates

acceleration causes the air resistance to increase

resultant force decreases to zero

so the skydiver falls at terminal velocity (no resultant force, as forces are equal in magnitude)

RESULTANT FORCE IS UPWARDS
OBJECT ACCELERATES UPWARDS AS SURFACE AREA OF PARACHUTE CAUSES AIR RESISTANCE TO INCREASE -> VELOCITY DECREASES -> AIR RESISTANCE DECREASES (FEWER COLLISIONS PER SECOND)

28
Q

Stopping

A

Thinking + Braking

29
Q

Thinking distance

A

Reaction time
Speed

30
Q

Reaction time

A

Distractions reducing concentration up
Tiredness up
Drugs up or down
Alcohol up

31
Q

Braking distance

A

Speed
Quality of brakes
Quality of tyres
Surface conditions
Road going downhill
Increased mass of passengers

32
Q

Braking energetics

A

When brakes pads push on wheels, transfers energy mechanically via friction

Decreases wheel’s eke

Increases thermal store

Therefore: If deceleration too high, overheating means driver loses control of vehicle. Therefore: Maximum braking force

33
Q

Conservation of momentum

A

Eeeuuhh momentum is always conserved 💯

34
Q

Car safety 🐈

A

Increasing time taken for the collision, for the same change in momentum.

This decreases the force experienced.

35
Q

6 marks:

man in car
man crashes car
man wearing seatbelt
car (🐈) forgor 💀

what happens to the 🚗 and the 🐈 and the 🕴

A

🚗 experiences a force against its’ motion and decellerates
🚗 stops

🕴 continues moving @ high speed
🕴 increases time for collision, stopping him w less force than the car

🐈 continues moving @ high speed
🐈 hits windscreen where it experiences a force and comes to rest (in peace) (and pieces)