Topic 2: motions and forces

Question 1

what is a scalar quantity

Answer 1

A quantity with size and no direction

Question 2

what is vector quantity

Answer 2

a quantity with size and direction

Question 3

what are the 6 main vector quantities

Answer 3

velocity
displacement
acceleration
force
weight
momentum

Question 4

what are the 4 main scalar quantities

Answer 4

distance
speed
mass
energy

Question 5

what is velocity

Answer 5

speed in a stated direction

Question 6

how do you work out average speed?

Answer 6

average speed = distance (m) / time (s)

Question 7

what is the equation for acceleration

Answer 7

a= (v-u) / t

acceleration ( m/s^2) = change in velocity (m/s) ÷ time (s)

Question 8

How do you work out final velocity - initial velocity

Answer 8

v^2 - u^2 = 2 x a x X

Question 9

On a distance/time graph what does a curve represent

Answer 9

the object is accelerating/decelerating

Question 10

On a distance/time graph what does a horizontal line represent

Answer 10

the object is stationary

Question 11

what does the gradient of a distance/time graph represent

Answer 11

the velocity / speed

Question 12

what are the 2 things you can use to measure speed in an experiment

Answer 12

a stopwatch
a light gate
The Light Gate has an infrared transmitter and receiver that will detect an object passing through the ‘gate’.

Question 13

what is the average speed of walking and cycling

Answer 13

walking: 1.4m/s
cycling: 6m/s

Question 14

what is the value of acceleration due to gravity

Answer 14

9.8 m/s^2 (rounded to 10m/s^2)

Question 15

what does a curve mean on velocity/time graph

Answer 15

changing acceleration

Question 16

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

Answer 16

object is moving at a constant velocity

Question 17

what does a straight slope on velocity/time graph represent

Answer 17

constant acceleration

Question 18

state newton’s first law

Answer 18

if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.

Question 19

state Newton’s second law

Answer 19

f = m x a

force = mass x acceleration

Question 20

define weight and state the equation to work out weight

Answer 20

the weight of an object is force acting on it due to gravity

W = m x g
weight (N) = mass (kg) x gravitational field strength (N/kg)

Question 21

what happens to an object moving in a circular path at constant speed

Answer 21

its direction constantly changes.

A change in direction causes a change in velocity

Question 22

what is the force that keeps an object moving in a circle

Answer 22

a centripetal force

Question 23

what is inertial mass

Answer 23

a measure of how difficult it is to change the velocity of an object and it is defined as the ratio of force over acceleration

Question 24

what is Newton’s third law

Answer 24

every action has an equal and opposite reaction

Question 25

define momentum and state the equation for momentum

Answer 25

the quantity of motion of a moving body, measured as a product of its mass and velocity. p = m x v momentum(kg m/s) = mass (kg) x velocity(m/s)

Question 26

what happens to momentum in collisions

Answer 26

Momentum is conserved in collisions and explosions .

Question 27

what is conservation of momentum

Answer 27

momentum never changes in an isolated collection of objects. | the total momentum of a system remains constant.

Question 28

what does this mean: F = (mv - mu) / t

Answer 28

force(N) = change in momentum (kg m/s) ÷ time(s)

Question 29

main method of measuring human reaction times and typical results

Answer 29

dropping a ruler | reaction time is usually 0.2 - 0.3 seconds

Question 30

what is the stopping distance of a vehicle made up of

Answer 30

the sum of the thinking distance and the braking distance

Question 31

what factors can affect stopping distance

Answer 31

``` the mass of the vehicle the speed of the vehicle the driver’s reaction time the state of the vehicle’s brakes the state of the road the amount of friction between the tyre and the road surface ```

Question 32

what factors can affect drivers reaction time

Answer 32

``` speed driving experience physical and cognitive fitness distractions driving under the influence sleepiness acute illness stress ```

Question 33

dangers caused by large deceleration

Answer 33

over heated brakes | driver may lose control of vehicle

Question 34

how do you calculate work done

Answer 34

work done = force x distance