Y8

Question 1

what is acceleration?

Answer 1

acceleration is the rate at which an objects speeds up

Question 2

what is deceleration?

Answer 2

deceleration is the rate at which an object slows down

Question 3

what is the unit for acceleration?

Answer 3

the unit of acceleration is m/s/s (meters per second per second)

Question 4

what does a speed time graph tell us?

Answer 4

A straight line tells us that the object is moving with constant acceleration.The steeper the line on a time graph the larger the objects acceleration.A flat line on a speed time graph tells us the object is moving at a constant speed.

Question 5

What happens to an object when a resultant force acts on it the direction it is moving?

Answer 5

When a resultant force acts on a object in the direction it ins moving that object accelerates and its kinetic store increases

Question 6

what is the relationship between the size of an object’s acceleration and the resultant force acting on it?

Answer 6

The larger the resultant force acting on a object the larger that objects acceleration. Acceleration is directly proportional to resultant force. This means that if resultant force doubles acceleration doubles.

Question 7

What does a graph of acceleration against resultant force look like?

Answer 7

A graph of acceleration against resultant force will be a straight line through the origin

Question 8

what happens to a object when a resultant force acts on it in the opposite direction to its motion?

Answer 8

When a resultant force acts on an object in the opposite direction to motion that object will decelerate,its kinetic store will decrease and the thermal store of the surroundings will increase.

Question 9

When you push an object ,and then let go, why does it slow down?

Answer 9

The force used to push the object is a contact force so as soon as the object is out of your hands there is no longer any contact and therefore no push force.In the absence of friction this object would keep moving at a steady speed because there will be no resultant force on it. In reality the object will slow down because there is a resultant force acting on it in the opposite direction to its motion ; this is caused by friction between the object and the surface it is on.

Question 10

what does and acceleration of 1m/s/s mean?

Answer 10

An acceleration of 1m/s/s tells us that every second an objects speed increases by 1m/s

Question 11

how do we stop moving vehicles?

Answer 11

When we stop moving objects as cars, we use the brakes to apply on a force on the vehicle in the opposite direction to its motion

Question 12

why do we stop moving vehicles over a longer period of time?

Answer 12

we try the braking force over a long period of time because this means the speed is reduced more slowly and this results in a smaller deceleration.Smaller deceleration require smaller resultant forces.

Question 13

why do objects moving through air experience air resistance?

Answer 13

When objects move through air there are ar resistance forces that act on them because the object collides with air molecules.

Question 14

why do larger surface areas and faster speeds result in more air resistance?

Answer 14

The larger the surface area of the object and the faster it is moving the more air molecules it will collide with per second and larger the air resistance force it will experience.

Question 15

What is terminal velocity?

Answer 15

A falling object will accelerate to start with but then reaches a steady speed that we know as terminal velocity

Question 16

Why do falling objects reach terminal velocity?

Answer 16

An object dropped from a height accelerate downwards to start with because it’s weight is the only force acting on it and therefore there is a resultant force downwards. However, it will not accelerate forever as the air resistance force acting on it increases as it gets faster. Eventually the air resistance Force will equal the weight and at this point there will be no resultant force so the object cannot Accelerate any further - the objectives reach the steady speed known as terminal velocity.

Question 17

What energy transfers take place in an object falling at terminal velocity?

Answer 17

An object falling at terminal velocity is losing height so it’s gravitational store is decreasing however because it is not getting any faster It’s kinetic store doesn’t change. The energy lost from its gravitational store is transferred to the thermal store of the surroundings due to the work done by air resistance.