explaining motion

Question 1

what does velocity tell you about an object?

Answer 1

• speed
• direction of travel

idea of distance:
opposite direction = negative
changes in distance in 1 direction = positive

Question 2

what do you need to know to calculate an objects speed?

Answer 2

• distance

- time

Question 3

how do you calculate speed?

Answer 3

s x t

Question 4

what is instantaneous speed?

Answer 4

speed of an object at a particular point in time

Question 5

what 2 things of a distance time graph is a measure of the speed?

Answer 5

slope or gradient

steeper the slope, greater speed

Question 6

how can you calculate the speed of an object?

Answer 6

working out gradient of a displacement time graph:

Question 7

what is the instantaneous velocity?

Answer 7

speed together with an indication of direction

Question 8

what happens in a curvy distance time graph?

Answer 8

curved, speed changing

Question 9

what does a speed time graph show?

Answer 9

slope or gradient represents how quickly accelerating

steeper slope, faster speed increase

Question 10

why are speed time graphs used in lorry tachographs?

Answer 10

• don’t exceed speed limit

- rest for suitable amounts of time

Question 11

what are velocity time graphs?

Answer 11

quantity velocity has both speed and direction, change in either will cause change in velocity

a velocity time graph can have negative values for the velocity axis

Question 12

how can you calculate acceleration?

Answer 12

acceleration = change in speed/time taken

Question 13

what is a force?

Answer 13

2 objects interacting with each other

whenever 1 object exerts a force on another, experiences a force in return

Question 14

what are forces in an interaction pair?

Answer 14

• equal in size

- opposite in direction and act on diff objects

Question 15

what are some examples of forces?

Answer 15

gravity (weight):
- 2 masses attracted to each other

air resistance (drag):
- air slows down skydiver by pushing upwards against him 

rocket and engines:
- engine pushes gas back (action) + gas pushes rocket forward (reaction)

Question 16

what happens when an object is resting on a surface?

Answer 16

object pulled down onto surface by gravity

• surface pushes up on object with an equal force

called reaction of the surface

Question 17

what is friction?

Answer 17

when 2 objects try to slide past one another both objects experience a force that tries to stop them from moving

objects don’t have to moving to experience friction eg friction from car brakes stops it from rolling

Question 18

why are arrows used when drawing diagrams of forces?

Answer 18

• size of arrow represents size of force

- direction of arrow shows the direction of force

Question 19

what happens if more than 1 force acts on an object?

Answer 19

will…

• add up if acting in same direction
• subtract if acting in opposite direction

overall effect of adding or subtracting forces called resultant force

Question 20

what is momentum?

Answer 20

measure of the motion of an object

Question 21

how can you calculate momentum?

Answer 21

momentum = mass x velocity

if lorry and car travelling at same speed, lorry will have more momentum bc bigger mass

Question 22

if the resultant force acting on an object is 0, it’s momentum won’t change, so what is the object?

Answer 22

• stationary

- already moving, continue moving at a steady speed

Question 23

if the resultant force acting on an object is not 0, is causes a change of momentum in the direction of the force which could what?

Answer 23

• make a stationary object move
• increase/decrease speed of object
• change objects direction

Question 24

what does change in momentum depend on?

Answer 24

• size of resultant force

- length of time the force is acting on the object

Question 25

what do collisions do and what can they affect?

Answer 25

cause changes in an objects momentum

can affect:

• car
• passengers = injuries

Question 26

what are safety devices?

Answer 26

force of the impact on human body can be reduced by increasing time of the impact

purpose of..

• seat belts
• crumple zones
• air bags

Question 27

what do cars and bicycles have?

Answer 27

• driving force:
  produced by engine or energy of cyclist
• counter force:
  caused by friction

Question 28

what happens if the driving force is bigger, equal to, or smaller than the counter force?

Answer 28

bigger:
vehicle speeds up

equal to:
constant speed

smaller:
slows down

Question 29

what is kinetic energy?

Answer 29

moving object has kinetic energy

depends on:

• mass
• velocity

greater mass and velocity, more kinetic energy

Question 30

how can you calculate kinetic energy?

Answer 30

1/2 x mass x velocity2