3.1 Motion Flashcards
Speed
distance per unit time
Displacement
distance moved in particular direction from a reference point
Velocity
Displacemnt per unit time
Acceleration
Change in velocity per unit time
Area beneth velocity time graph?
Displacment
Grad of velocity time graph?
Acceleration
Grad of displacment time graph?
Velocity
If straight:constnat
if curved:accelerating/de
How do you answer suvat Q’s?
Write suvat down the side and use the equations on the sheet
acceleration on g of free fall
9.81ms-2
techniques and procedures used to determine the acceleration of free fall using trapdoor and electromagnet arrangement or light gates and timer
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
how to answer projectile motion Q with angle, height and velocity
V=21ms-1
angle=45.
Height=1.8m
- RESOLVE velocity into Horizontal and Vertical
Uh is 21cos45=14.84ms
Vh is 21sin45=14.84
2.Find Vv
=-15.99
- Find t
=3.144s - v=s/t
ah=0
14.84 x 3.144 = 46.7m
why do all objects fall at the same acceleration despite different masses
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.
instantaneous speed
Rate of change of displacement with respect to time at that instant
True or false
Horizontal time and vertical time are the same
True
What are the sign conventions for g u v t s
g Always downwards so usually negative u Positive or negative v Positive or Negative t always positive s positive or negative
How do you investigate what affects the motion of a trolley on a slope?
- To investigate how the distance a trolley has rolled affects its speed, set up the experiment shown in (draw diagram)
- Measure length of trolley
3.mark a start line on the ramp
(to make sure the trolley always starts at same position)
- Measure the angle of the ramp and the distance from the start line to the light gate, d.
- Line up trolley with start line , Let go of it so the initial velocity is 0
- 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
- Change start position of trolley so d is varied
- 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
How do you investigate how collisions affect the motion of a trolley?
(Trolley with wall)
- 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
- Measure length of trolley
- Turn on video camera and start recording
- Line up trolley with start line, let go so initial velocity is 0
- Once trolley has hit wall and is at rest stop recording
How do you investigate final velocities of 2 trolleys colliding?
- Set up experiment as shown in diagram (metre ruler and smooth surface) and set up video camera perpendicular to direction of trolley travel
- Measure length of both trolleys
- Turn on video camera and start recording
- Push one trolley so it hits second trolley
- Stop recording when both trolley come to rest
How do you use both of the motion trolley experiments to investigate how mass and velocity just before collision affects velocities/velocity after collision?
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
Stopping distance=
Thinking distance + breaking distance
Reaction time
time your body takes to react and hit the breaks after seeing a hazard
thinking distance
the distance the vehicle travels during the drivers reaction time
Braking distance
the distance the vehicle travels after the brakes are applied until it come to stop
Thinking distance=
speed x reaction time
Reaction time is increased by:
Tiredness
alcohol or other drug use
illness
distractions
Braking distance depends on:
Braking force, friction between tyres and the road, the mass and the speed
Breaking force is reduced by:
Reduced friction between brakes and wheels (worn or badly adjusted brakes)
Friction between tyres and road is reduced by:
wet or icy roads, leaves or dirt on road, worn out tyre treads
Mass is affected by:
Size of car and what you put in it
braking distance is proportional to?
v^2
or
mass
How do seat belts help drivers? (3marks)
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
