3.1 Motion

Question 1

Speed

Answer 1

distance per unit time

Question 2

Displacement

Answer 2

distance moved in particular direction from a reference point

Question 3

Velocity

Answer 3

Displacemnt per unit time

Question 4

Acceleration

Answer 4

Change in velocity per unit time

Question 5

Area beneth velocity time graph?

Answer 5

Displacment

Question 6

Grad of velocity time graph?

Answer 6

Acceleration

Question 7

Grad of displacment time graph?

Answer 7

Velocity
If straight:constnat
if curved:accelerating/de

Question 8

How do you answer suvat Q’s?

Answer 8

Write suvat down the side and use the equations on the sheet

Question 9

acceleration on g of free fall

Answer 9

9.81ms-2

Question 10

techniques and procedures used to determine the acceleration of free fall using trapdoor and electromagnet arrangement or light gates and timer

Answer 10

Trapdoor electromagnet:
Measure h from bottom of ball bearing to trapdoor

Flick switch to simultaneously start the timer and disconnect the electromagnet releasing ball bearing

Ball bearing falls, knock trapdoor breaking circuit stopping timer

use h=1/2gt^2
to find g

source of error: measurement of h uncertainty 1 mm

Question 11

how to answer projectile motion Q with angle, height and velocity

V=21ms-1
angle=45.
Height=1.8m

Answer 11

1. RESOLVE velocity into Horizontal and Vertical
   Uh is 21cos45=14.84ms
   Vh is 21sin45=14.84

2.Find Vv
=-15.99

3. Find t
   =3.144s
4. v=s/t
   ah=0
   14.84 x 3.144 = 46.7m

Question 12

why do all objects fall at the same acceleration despite different masses

Answer 12

a uniform field has a constant value 9.81N/Kg near the surface area of earth.

A heavier object that has a greater downward force acting on it in direct proportion to its mass (W=mxg); however acceleration is inversely proportional to mass (Newtons 2nd law).

Hence the 2 effects cancel out and all masses have same acceleration.

Question 13

instantaneous speed

Answer 13

Rate of change of displacement with respect to time at that instant

Question 14

True or false

Horizontal time and vertical time are the same

Answer 14

True

Question 15

What are the sign conventions for
g
u
v
t
s

Answer 15

g Always downwards so usually negative
u Positive or negative
v Positive or Negative
t always positive
s positive or negative

Question 16

How do you investigate what affects the motion of a trolley on a slope?

Answer 16

1. To investigate how the distance a trolley has rolled affects its speed, set up the experiment shown in (draw diagram)
2. Measure length of trolley

3.mark a start line on the ramp
(to make sure the trolley always starts at same position)

4. Measure the angle of the ramp and the distance from the start line to the light gate, d.
5. Line up trolley with start line , Let go of it so the initial velocity is 0
6. The data logger will record the time taken for the trolley to pass through the light gate and calculate the velocity of the trolley as it passes through the gate
7. Change start position of trolley so d is varied
8. Repeat experiment for each distance 3 times and average the recorded velocities to reduce the error in your final result.

To investigate other factors keep d the same and change either:
Angle
Mass of trolley
Shape/ size of trolley
ramp material

Question 17

How do you investigate how collisions affect the motion of a trolley?
(Trolley with wall)

Answer 17

1. Set up experiment as shown in diagram (smooth ramp then metre ruler then wall) and set up video camera perp to direction of trolley travel
2. Measure length of trolley
3. Turn on video camera and start recording
4. Line up trolley with start line, let go so initial velocity is 0
5. Once trolley has hit wall and is at rest stop recording

Question 18

How do you investigate final velocities of 2 trolleys colliding?

Answer 18

1. Set up experiment as shown in diagram (metre ruler and smooth surface) and set up video camera perpendicular to direction of trolley travel
2. Measure length of both trolleys
3. Turn on video camera and start recording
4. Push one trolley so it hits second trolley
5. Stop recording when both trolley come to rest

Question 19

How do you use both of the motion trolley experiments to investigate how mass and velocity just before collision affects velocities/velocity after collision?

Answer 19

Use video analysis software to view clip frame by frame. Pick a point on metre stick and count how many frames it takes a trolley to pass that point

By knowing frames per second of camera, calculate time taken (t) for the trolley to pass the point, use length of trolley (L) to calculate velocity

Time taken for trolley to pass point = No. of frames for trolley to pass point x 1 second/ Frame rate of camera

Velocity= L/t

Question 20

Stopping distance=

Answer 20

Thinking distance + breaking distance

Question 21

Reaction time

Answer 21

time your body takes to react and hit the breaks after seeing a hazard

Question 22

thinking distance

Answer 22

the distance the vehicle travels during the drivers reaction time

Question 23

Braking distance

Answer 23

the distance the vehicle travels after the brakes are applied until it come to stop

Question 24

Thinking distance=

Answer 24

speed x reaction time

Question 25

Reaction time is increased by:

Answer 25

Tiredness
alcohol or other drug use
illness
distractions

Question 26

Braking distance depends on:

Answer 26

Braking force, friction between tyres and the road, the mass and the speed

Question 27

Breaking force is reduced by:

Answer 27

Reduced friction between brakes and wheels (worn or badly adjusted brakes)

Question 28

Friction between tyres and road is reduced by:

Answer 28

wet or icy roads, leaves or dirt on road, worn out tyre treads

Question 29

Mass is affected by:

Answer 29

Size of car and what you put in it

Question 30

braking distance is proportional to?

Answer 30

v^2
or
mass

Question 31

How do seat belts help drivers? (3marks)

Answer 31

Increases time (of impact / to slow down) / increases
the distance (travelled by the driver)

Smaller deceleration / acceleration

Force is smaller because F=ma and a is smaller

or force is smaller because F = Ek/x and x is bigger

or force is smaller because F=change p/change t and t is bigger