TOPIC 2 FORCES AND MOTION

Question 1

how do you work out average speed

Answer 1

speed = distance/time

Question 2

what are the units for average speed

Answer 2

metres/second

Question 3

if an object travels at a constant speed what else stays the same

Answer 3

it is also travelling the same distance every second

Question 4

why do we use average speed?

Answer 4

we use average as the speed may vary during the journey.

Question 5

on a distance/time graph what does a steeper gradient represent

Answer 5

the object is travelling faster

Question 6

on a distance/time graph what does a horizontal line mean

Answer 6

it means the object is stationary

Question 7

on a distance/time graph what does a curved line represent

Answer 7

it means the speed of the object is increasing (changing)

Question 8

how do you work out speed from a distance time graph

Answer 8

speed=gradient- yaxis/xaxis

Question 9

is speed scalar or a vector quantity

Answer 9

speed is a scalar quantity

Question 10

what is a scalar quantity?

Answer 10

something that only measures magnitude e.g speed

Question 11

what is a vector quantity?

Answer 11

something that measure both magnitude and direction

Question 12

is velocity a speed or a vector quantity

Answer 12

vector

Question 13

what is the equation for acceleration using velocity and time

Answer 13

acceleration = change in velocity/ time taken

Question 14

what is does the gradient of a velocity time graph represent

Answer 14

acceleration

Question 15

what does the area under a velocity time graph represent ?

Answer 15

the distance travelled

Question 16

how can you use an experiment to investigate the motion of objects (toy car or tennis ball…)

Answer 16

the light gate experiment

Question 17

how do you set up a light gate experiment

Answer 17

set up a ramp of about 15degrees

measure out the length of the object(a card)

set up a single light gate at the bottom of the track and connect to a data logger and get it to record speed.

allow the trolley to run down the ramp

measure the distance travelled by the trolley release point and the light gate

use a stop watch to measure how long the trolley takes to travel between these two points

record speed from the data logger

Question 18

how does a light gate calculate speed

Answer 18

the light gate starts a timer - it measures how long the beam of light is broken for and if we know the length of the card (in metres) we can calculate speed.

Question 19

what are the errors with the light gate experiment

Answer 19

The reaction time from the stop watch and the judgement of when it goes through the beam

The experiment uses speed = distance/time however the trolley accelerates

There could be human error in measuring distance and error in releasing the trolley

Question 20

what does a horizontal line on a velocity time graph?

Answer 20

the object is travelling at a constant speed

Question 21

what are the units for any force

Answer 21

newtons (N)

Question 22

what is a force ?

Answer 22

a force is a push or a pull - it can change shape, speed and direction of the object

Question 23

name some examples of forces

Answer 23

Gravity, Electrostatic, Thrust, Drag, Lift, Tension, Magnetic, Friction.

Question 24

is force a vector or scalar quantity

Answer 24

vector

Question 25

what is the equation for force

Answer 25

f = mass x acceleration

Question 26

what is the equation for weight

Answer 26

weight = mass (kg) x acceleration (due to gravity)

Question 27

what are the units for weight?

Answer 27

N/kg

Question 28

what is the difference between weight and mass

Answer 28

weight is a force and depends of the strength of gravity whereas mass is the amount of matter and does not change

Question 29

what are the units for acceleration

Answer 29

m/s2

Question 30

what is newtons 1st law?

Answer 30

Objects will stay stationary or continue to move with a constant speed, unless an unbalanced force acts upon them

Question 31

what is newtons 2nd law?

Answer 31

The acceleration produced by a force when it acts on a body is proportional to the force and takes place in the same direction as the force

Question 32

what is newtons 3rd law?

Answer 32

To every force there is an equal and opposite reaction force

Question 33

describe the forces acting on a falling object and why they reach terminal velocity

Answer 33

Initially the only force acting is weight so there is a resultant force downwards and therefore it will accelerate. The speed will increase and therefore drag will increase resulting in the resultant force to decrease. Eventually weight will equal drag which means that the resultant force will equal 0 meaning the object has reached terminal velocity.

Question 34

in a falling skydiver, what forces are acting

Answer 34

weight is pulling him towards the floor and resistance (drag) is acting against the skydiver upwards

Question 35

how does shape and area affect a falling object

Answer 35

Drag depends on shape and area. For example; a skydiver Without a parachute open they have a small area and a force equal to the weight- but with a parachute they have a much larger area. There is a much larger force of drag or air resistance acting on the body and in comparison a smaller weight force pulling them down so this means terminal velocity will lower.

Question 36

describe friction

Answer 36

friction is a force which opposes motion. Friction occurs in many ways on objects - with static motion on solid gripping surfaces, sliding friction when solid surfaces move past each other or resistance in liquids and gases (more drag on an object the slower it can move) - friction always increases when the speed of the object increases

Question 37

Name the safety features of a car

Answer 37

Crumple zones Seat belt Air bag

Question 38

How do crumple zones reduce the impact forces on passengers

Answer 38

They absorb the kinetic energy of the crash , work = force x distance - a large stopping distance reduces the stopping force Force= mass x acceleration increasing stopping time and reduces deceleration and therefore also reducing the force

Question 39

How do seat belts reduce impact forces on passengers

Answer 39

According to newtons first law "an object will stay stationary or move at a constant velocity unless acted on by an unbalanced force". The flexible material increases stopping distance, this reduces acceleration (F=ma) and (F=mv/t) and makes stopping distance smaller. It prevents contact with the steering wheel and windscreen. Also the seatbelt covers the sturdy parts of your body e.g. pelvis and chest meaning there is a large surface area covered and reduces pressure