Forces pt3

Question 1

What Newton’s second law?

Answer 1

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

Question 2

What is the acceleration?

Answer 2

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

Question 3

What is the equation that connects force mass and acceleration?

Answer 3

Force = mass x acceleration

Question 4

The equation of acceleration

Answer 4

acceleration = change in velocity/ time taken

Question 5

What is inertia?

Answer 5

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

Question 6

What is a measure of inertia?

Answer 6

mass

Question 7

How is the inertial mass found?

whats the equation

Answer 7

m = f/a

Question 8

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

Answer 8

bigger

Question 9

Describe what terminal velocity is

Answer 9

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

Question 10

What is Newton’s Third Law?

Answer 10

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

(Every action has an equal and opposite reaction)

Question 11

What is the equation for momentum?

Answer 11

momentum = mass x velocity

p = mv

Question 12

When does a change in momentum occur?

Answer 12

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

Question 13

What type of quantity is momentum?

Answer 13

vector

Question 14

What is the conservation of momentum?

Answer 14

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

Question 15

Stopping distance = ______ + _________

Answer 15

braking + thinking distance

Question 16

What is thinking distance is affected by?

Answer 16

• speed: the faster the more distance you will cover

- reaction time: longer reaction time, longer thinking distance

Question 17

What affects reaction time

Answer 17

Distraction, drugs and alcohol increase reaction time

caffeine decreases it

Question 18

What is braking distance is affected by?

Answer 18

• 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

Question 19

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

Answer 19

• 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

Question 20

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

Answer 20

brakes overheating or loss of control

Question 21

How do you find the size of the braking force?

Answer 21

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

Question 22

What do safety features in cars do?

Answer 22

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.

Question 23

How do seatbelts work?

Answer 23

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.

Question 24

How do airbags work?

Answer 24

• 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.

Question 25

Name car safety features

Answer 25

• airbags
• crumple zones
• seat belts

Question 26

How do crumple zones work?

Answer 26

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.

Question 27

How do cycle helmets work?

Answer 27

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

reduces the impact on your brain

Question 28

How do crash mats and cushioned playground flooring work?

Answer 28

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

made from soft, compressible materials