P2.1 Forces and their effects

Question 1

Understand that forces work in pairs

Answer 1

For every force there is an equal and opposite one. They must be of the same type (i.e. gravity … Earth exerts a gravitational force on you, you exert a gravitational force on the earth). Not to be confused with balanced forces (i.e. gravity pulls you down you experience a reaction force from the ground which is equal in size, balanced hence you don’t move

Question 2

What a resultant force is and how to calculate it

Answer 2

The sum of all the forces acting on a body

Question 3

Understand about equal and opposite forces

Answer 3

For every force there is an equal and opposite one. They must be of the same type (i.e. gravity … Earth exerts a gravitational force on you, you exert a gravitational force on the earth). Not to be confused with balanced forces (i.e. gravity pulls you down you experience a reaction force from the ground which is equal in size, balanced hence you don’t move

Question 4

Describe how a change in the resultant causes changes to motion

Answer 4

Newton’s first & second law can be used to explain this. Newton’s first states objects will continue at constant velocity (or at rest) unless another external force acts on it. Newton’s second F=ma shows us that is there is a resultant force the result will be acceleration (or deceleration)

Question 5

Be able to draw and interpret Distance- time graphs So what does it mean if the graph is flat? What does it mean if it is sloped? What does it mean if it is curving?

Answer 5

Tell the story from a distance time graph. So what does it mean if the graph is flat? No movement/stationary What does it mean if it is sloped? Constant velocity What does it mean if it is curving? Acceleration

Question 6

Understand the difference between speed and velocity (HT)

Answer 6

Speed only has magnitude no direction Velocity has magnitude and direction Objects travelling in a straight line but in opposite direction at the same speed of 10m/s then one will have a velocity of 10m/s and one will have a velocity of -10m/s

Question 7

Calculate the speed of an object from the gradient of a distance-time graph (HT)

Answer 7

Steeper the slope the faster it’s speed is

Question 8

Be able to calculate acceleration when given the formula Acceleration = change in speed / time Force = mass x acceleration (can you rearrange this one for acceleration?)

Answer 8

Acceleration = Force / mass

Question 9

Be able to draw and interpret velocity time graphs So what does it mean if the graph is flat? What does it mean if it is sloped? What does it mean if it is curving?

Answer 9

So what does it mean if the graph is flat? Constant velocity What does it mean if it is sloped? Constant acceleration What does it mean if it is curving? Increasing (or decreasing) acceleration

Question 10

Calculate the acceleration of an object from the gradient of a velocity-time graph (HT)

Answer 10

Steeper the slope the faster the acceleration Downward slope means it is decelerating

Question 11

Calculate the distance an object travelled from a velocity-time graph (HT)

Answer 11

Area under the graph = distance travelled

Question 12

Be able to use the equation relating force, mass and acceleration, F=ma Can you rearrange it for mass and acceleration?

Answer 12

mass = force / acceleration acceleration = force / mass

Question 13

Explain reaction time

Answer 13

The time it takes you to think and react to the situation. I.e. you see an incident you think about braking, your body sends an impulse to you leg to brake

Question 14

Explain the difference between thinking distance, braking distance and stopping distance

Answer 14

thinking distance is the distance you travel during the reaction time. In this time your speed has not changed (you are not braking yet) Braking distance - the distance it takes you to stop the car Stopping distance = thinking distance + braking distance

Question 15

Describe how stopping distance is linked to speed

Answer 15

Faster you go the longer the stopping distance is

As you can see from 30 to 60 the speed doubles but the stopping distance goes up nearly 4 times

Question 16

Recall the factors that affect a drivers ability to react

Answer 16

How awake they are?

Are they under the influence of any type of drugs?

Distractions … using a mobile phone, etc.

Question 17

Recall the factors that affect braking distance

Answer 17

Road condition

Weather

State of the tyres

State of the brakes

Question 18

Know which forces act on an object moving in a fluid

Answer 18

Weight (force of gravity pulling it down)

Air resistance or drag (the faster the object moves the larger this becomes)

Question 19

Describe and explain how velocity changes as an object moves through a fluid

Answer 19

Velocity will initially increase rapidly (acceleration), as speed increases so drag will to this will slow down the acceleration until both forces are balanced. Once they are balanced it has reached terminal velocity