Chapter 3-motion Definitions

Question 1

Average speed

Answer 1

The rate of change in distance calculated over a complete journey.
(distance/time)
( gradient of distance-time graph)
units: ms-1

Question 2

Instantaneous speed

Answer 2

The speed over an infinitesimal interval of time.

found by drawing tangent to draw at certain time
(greater gradient–> greater instantaneous speed)
unit: ms-1

Question 3

Scalar quantity

Answer 3

A quantity with magnitude but no direction

e.g. speed, distance, time

Question 4

Vector quantity

Answer 4

A quantity with both magnitude and direction

e.g. velocity, displacement

Question 5

Average velocity

Answer 5

the change in displacement for a journey divided by time taken

(delta displacement/ delta time)
(is gradient of displacement-time graph)
units:ms-1

Question 6

Acceleration

Answer 6

The rate of change of velocity of an object

a=v/t
gradient of velocity-time graph
units: ms-2

Question 7

Displacement

Answer 7

the distance travelled in a particular direction

vectors quantity
(displacement =area under velocity-time graph)
unit: m

Question 8

Momentum

Answer 8

is product of mass and velocity

units=kgms-1

Question 9

acceleration of free fall

Answer 9

the rate of change of velocity of an object falling in a gravitational field

symbol: g
value: 9.81 ms-2

Question 10

Air resistance

Answer 10

The drag or resistive force experienced by objects moving through air

Question 11

stopping distance

Answer 11

The total distance travelled from the time when a driver first sees a reason to stop to time when vehicle stops.

sum of thinking distance and braking distance.

Question 12

Thinking distance

Answer 12

The distance travelled by a vehicle from when the driver first perceives a need to stop to when the brakes are applied

thinking distance = speed* reaction time

(affected by alertness of driver)

Question 13

Braking distance

Answer 13

distance travelled by a vehicle from the time the brakes are applied until the vehicle stops.

affected by: speed of vehicle
conditions of brakes, tyres and road
weather conditions

Question 14

Free fall

Answer 14

The motion of an object accelerating under gravity with no other force acting on it

Question 15

Projectiles

Answer 15

An object that is thrown or propelled on the surface of the Earth

(for projectile motion–> assume no air resistance)

Question 16

Time of flight

Answer 16

The time taken for an object to complete it’s motion
units: seconds

(double vertical max height time)

Question 17

Base unit

Answer 17

one of seven units that form the building blocks of the SI measurement system