CP2- Forces And Motion

Question 1

how do you work out the resultant force on a force diagram?

Answer 1

• if the forces are acting in the same direction, add them
  if the forces are acting in different directions, take away

Question 2

what is the resultant force?

Answer 2

• the single force that has been produced as a result of two that are acting together

Question 3

what is a balanced force?

Answer 3

• when all resultant forces on an object are 0
• will not change the velocity of am object

Question 4

what is an unbalanced force?

Answer 4

• there is non-zero resultant force on an object
• this non-zero resultant force will always produce acceleration or deceleration in the direction of the resultant force

Question 5

what is newtons 1st law?

Answer 5

• a moving object will continue to move at the same speed and direction if the resultant force is zero unless an external force acts on it
• a stationary object will remain at rest unless and external force acts on it
• a resultant force is needed to make something slow down, speed up, start moving or stop

Question 6

what is the relationship between the resultant force and acceleration?

Answer 6

• the larger the resultant force the more the object accelerates
• they are directly proportional

Question 7

what is the relationship between acceleration and mass?

Answer 7

• they are inversely proportional
• an object with larger mass will accelerate less than one with a smaller mass

Question 8

what is newtons second law?

Answer 8

the acceleration in the direction of the resultant force depends on the size of the force and the mass of the object.

Question 9

what equation links to newtons second law?

Answer 9

force = mass x acceleration

Question 10

what is the centripetal force?

Answer 10

• when an object moves in a circle there is changing velocity, so this means that it is accelerating. so there is a resultant force which acts towards the centre of the circle
• this is called the centripetal force

Question 11

what is mass?

Answer 11

• quantity of matter there is in an object
• measured in kg
• scalar quantity
• can use a scale to measure

Question 12

what is weight?

Answer 12

• a measure of the pull of gravity on an object which depends on the gravitational field strength
• measured in newtons since it is a force
• can use a force meter

Question 13

what is earths gravitational field strength?

Answer 13

10N

Question 14

what is the equation for weight?

Answer 14

weight = mass x gravitational field strength

Question 15

what is inertia?

Answer 15

• the tendency for motion to remain unchanged
• for example newtons 1st law which involves an object having a constant velocity unless there is an external force, the tendency for the object to keep moving with this constant velocity is inertia

Question 16

what is the inertial mass?

Answer 16

• since larger objects take greater force to change the velocity, the inertial mass is a measure of how difficult it is to change the velocity of an object

Question 17

how can you find the inertial mass?

Answer 17

rearrange the f=ma formula to m=f/a

Question 18

what is newtons third law?

Answer 18

when two objects interact, the forces they exert on each other are equal and opposite
- this can happen with physical objects or at a distance for example the gravitational attraction between the earth and moon

Question 19

what are action-reaction forces?

Answer 19

two of the same type forces that are the same size and in opposite directions, however they are NOT the same as balanced forces

Question 20

how to action reaction forces differ from balanced forces?

Answer 20

• action reaction forces act on different objects whereas balanced forces occur on the same object
• although two objects may have the same action reaction force after colliding, they usually have different masses so will react differently in terms of acceleration

Question 21

what is momentum?

Answer 21

• a measure of the tendency of an object to keep moving or how hard it is to stop moving
• momentum depends on mass and velocity
• the greater the mass or velocity the more momentum it has

Question 22

what is the equation for momentum?

Answer 22

momentum = mass x velocity

Question 23

what is the conservation of momentum?

Answer 23

• in a closed system the total momentum before an event is the same as after an event
• for example if a moving ball collides into a stationary ball, it will start moving and the initial moving ball will share its momentum

Question 24

equation for force involving momentum and velocity.

Answer 24

F= m(v-u) / t

Question 25

what is the thinking distance?

Answer 25

the distance a car travels when a driver realises the problem and reacts

Question 26

what is the braking distance?

Answer 26

the distance taken to stop once the brakes have been applied

Question 27

what is the stopping distance?

Answer 27

the sum of the thinking and braking distance, the overall time for a driver to identify the danger and completely stop

Question 28

what factors affect the thinking distance?

Answer 28

- reaction time which can be affected by alcohol, drugs, fatigue and distractions - speed- the faster a vehicle is travelling the further it will travel during the thinking distance

Question 29

what factors affect the braking distance?

Answer 29

- speed- faster speeds makes it longer to stop - mass of the car- people or objects in a vehicle increases the momentum which takes a larger force to stop - condition of brakes, worn brakes can't provide as much force and brakes in good condition - friction between tyre and road

Question 30

what are crumple zones?

Answer 30

- during collisions, vehicles will come to a stop very quickly so there is a larger force acting on the car and passengers - to lower this force you need the car to decelerate by making it slow down over a long time - crumples zones increase collision time, therefore reducing the force and reducing the risk of injury

Question 31

how are car airbags effective?

Answer 31

increases the time taken for someone to collide with the car

Question 32

How does Mass affect action reaction forces?

Answer 32

- Although the same size force is being exerted on each object if they collide, objects with smaller masses will accelerate farther