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AQA Physics > Forces pt3 > Flashcards

Forces pt3 Flashcards

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1
Q

What Newton’s second law?

A

The acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object.

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2
Q

What is the acceleration?

A

a measure of how quickly an object speeds up, slows down or change direction

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3
Q

What is the equation that connects force mass and acceleration?

A

Force = mass x acceleration

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4
Q

The equation of acceleration

A

acceleration = change in velocity/ time taken

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5
Q

What is inertia?

A

the tendency for objects to continue in the same state of motion

it is how difficult it is to change the velocity of an object

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6
Q

What is a measure of inertia?

A

mass

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7
Q

How is the inertial mass found?

whats the equation

A

m = f/a

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8
Q

The larger the mass, the _____ the force needed to change the velocity

A

bigger

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9
Q

Describe what terminal velocity is

A

When an object falls through a fluid :

1) At first the object accelerates due to the force of gravity
2) As it speeds up, the resistive forces increases
3) The resultant force reaches zero when the resistive forces balance the force of gravity

At this point, the object will fall at a steady speed = terminal velocity

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10
Q

What is Newton’s Third Law?

A

Whenever two objects interact, the forces they exert on each other are equal and opposite.

(Every action has an equal and opposite reaction)

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11
Q

What is the equation for momentum?

A

momentum = mass x velocity

p = mv

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12
Q

When does a change in momentum occur?

A

When a force acts on an object that is moving, or able to move

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13
Q

What type of quantity is momentum?

A

vector

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14
Q

What is the conservation of momentum?

A

In a closed system, the total momentum before an event is equal to the total momentum after the event.

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15
Q

Stopping distance = ______ + _________

A

braking + thinking distance

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16
Q

What is thinking distance is affected by?

A
  • speed: the faster the more distance you will cover

- reaction time: longer reaction time, longer thinking distance

17
Q

What affects reaction time

A

Distraction, drugs and alcohol increase reaction time

caffeine decreases it

18
Q

What is braking distance is affected by?

A
  • Your speed: faster the vehicle, longer it takes to stop
  • Adverse weather cnditions = less friction = skid
  • condition of tyres: if tyres are bald then they cannot get rid of water in wet conditions. this leads to them skidding on top of the water
  • Brakes
  • condition of vehicles
19
Q

What happens when a force is applied to the brakes of a vehicle?

A
  • work is done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brake increases
20
Q

What could large decelerations ( caused by a great braking force) lead to?

A

brakes overheating or loss of control

21
Q

How do you find the size of the braking force?

A

work done ( kinetic energy) = force x distance (braking distance

22
Q

What do safety features in cars do?

A

These features reduce injuries to the people in the car by absorbing kinetic energy from the impact.

They increase the time taken for the change in momentum on the occupants’ bodies, and so reduce the forces involved and any subsequent injuries.

These features absorb energy when they change shape. This reduces injuries to the people in the car.

23
Q

How do seatbelts work?

A

stop you tumbling around inside the car if there is a collision.

However, they are designed to stretch a bit in a collision. This increases the time taken for the body’s momentum to reach zero, and so reduces the forces on it.

24
Q

How do airbags work?

A
  • increase the time taken for the head’s momentum to reach zero, and so reduce the forces on it.
  • They also act a soft cushion and prevent cuts.
25
Q

Name car safety features

A
  • airbags
  • crumple zones
  • seat belts
26
Q

How do crumple zones work?

A

Crumple zones are areas of a vehicle that are designed to crush in a controlled way in a collision.

They increase the time taken to change the momentum of the driver and passengers in a crash, which reduces the force involved.

27
Q

How do cycle helmets work?

A

contain a crushable layer of foam = lengthen the time taken for your head to stop in a crash

reduces the impact on your brain

28
Q

How do crash mats and cushioned playground flooring work?

A

increase the time taken for you to stop if you fall on them

made from soft, compressible materials

AQA Physics (22 decks)

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