Section 1- Motion And Forces Flashcards
What’s a vector quantity ?
Examples
Have magnitude (size) and direction
Force, velocity , displacement,acceleration etc
What’s a scalar quantity ?
Examples
Only have magnitude but no direction
Speed, distance , mass , energy
Scalar or vector?
Distance
Displacement
Speed
Velocity
Distance - scalar
Displacement - vector
Speed- scalar
Velocity- vector
Equation for distance travelled ..
Distance travelled = average speed (m/s) X time (s)
Average speed of walking,running, cycling
Walking - 1.4m/s
Running- 3m/s
Cycling- 5.5m/s
2 types Equipment to measure distance and time. When they’re useful
Light gates- short time intervals, get rid of bad human reaction time
Rolling tape measure- measure a persons walking speed
Equation for acceleration…
a=(v-u) /t
(Final velocity- initial velocity) / time
What’s acceleration ?
Rate of change of velocity
What’s constant acceleration sometimes called?
Uniform acceleration
What is the acceleration due to gravity ? xm/s
10m/s
equation of uniform acceleration…
What’s uniform acceleration?
V^2-U^2=2 X A X distance
Final velocity- initial velocity= 2 X acceleration X distance
If an objects velocity is increasing at a steady rate
What is Newton’s first law?
A resultant force is needed to make something start moving,speed up or slow down
What will happen if the resultant force on a moving object is 0?
It will remain moving at the same velocity
What will a non-zero resultant force produce ?
Acceleration or deceleration in the direction of force
What’s the force that keeps something moving in the centre of a circle?
Centripetal force
What is acceleration inversely proportional to?
The mass of an object.
Newton’s second law formula…
F=m X a
Force = mass X acceleration
What is inertia?
The tendency for a motion to remain unchanged.
How do we find inertial mass?
Rearranging Newton’s second law
m=F/a
What is Newton’s third law?
When two objects interact, the forces they exert on each other are equal and opposite
What’s equilibrium
a state in which opposing forces or influences are balanced.
Investigating motion core practical.
What does it test?
Newton’s second law F=mXa
How to carry out the investigating motion practical
1.Measure mass of trolley,unit masses and hanging hook.measure length of card which will interior light gate beams. Set up apparatus
2.adjust height of ramp until trolley starts to move.
3.mark a line on the ramp just before the light gate. Light gate will record initial speed of the trolley as it begins to move
4. Attatxh trollet to hanging mass by the string. Hold the trollet still at the start line.let it go do it rolls down the slope
5.the weight of the hook and any masses attached to it will provide accelerating force equal to the mass of the hook X gravity
6. The light gates wil record the speed of the trolley as it passes through. Then do the equation a-(v-u)/t
7. Repeat 3 times and calculate avaradhe acceleration
How do we investigate how the mass of the system affects acceleration ?
Add masses one at a time to the trolley
When you add mass calculate the systems acceleration
What changes in the experiment and what stays the same?
Mass of trolley and hook changes
Total mass stays the same
How do we measure weight
Calibrated spring (newton meter)
How do we calculate weight?
Weight (N) = mass (kg) X gravitational field strength (n/kg)
How do we calculate momentum? Isit scalar or vector?
Unit for momentum…
Mass X velocity. p=m X v
Vector
Kg m/s
What’s momentum before and after an event like in a closed system like a collision.
The total momentum before and after an event is the same.
This is callled conservation of momentum
Momentum before =
Momentum before = momentum after
What happens when a resultant force acts on an object?
The objects momentum changes
Equation for force…
Force =(mv-mu)/t
Force = change in momentum /time
What does a fast change In momentum mean ?
A big force acting on it
Example of change in momentum and force interlinking…
In a car crash someone’s momentum changes very fast, this means they’re under a bigger force will will cause more injury
test to check reaction time…
Ruler drop test
How to carry out the ruler drop test?
1.Sit with your arm resting on the edge of a table(stops you from moving arm up or down). Get someone to hold a ruler between your thumb and forefinger lined with zero.
2.without warning,the person holding the ruler should drop it. Close thumb. And finger to try catch is as quick as possible
3.measurement of ruler howfrom 0 is how is how far the ruler dropped in the time you reacted
4.the longer the distance, the longer the reaction time
5.. repeat a few times and take mean reaction time.
How to calculate stopping distance?
Stopping distance= thinking distance +braking distance
What is thinking distance ?
Distance the car travels in the time it takes the driver to notice the hazard and apply the brakes
What’s the braking distance ?
Distance to stop once brakes have been applied
Factors affecting thinking distance…
Speed
Reaction time
Factors affecting braking distance…
Speed
Friction between tyres and road
How good your brakes are
Mass of the car
Why are large decelerations dangerous ? How to lower the force?
Because they require a lot of force so can cause serious injuries
To lower the force slow the object over a long period of time
Features in a car that increases collision times …
Seatbelt
Airbag
How to calculate distance ?
Distance = Speed X Time
How to calculate acceleration
Acceleration = final velocity - initial velocity / time
How to calculate force ?
Force = mass X acceleration
How to calculate weight ?
Weight = mass X gravitational field strength
How to calculate gpe?
GPE= Mass X gravity X height
How to calculate momentum
Momentum = Mass X Velocity
