Topic 2- Motion and Forces Flashcards
What is the difference between Scalar and Vector quantities?
- They both have magnitude (number)
- Vector has a direction
Recall 4 scalar quantities
- Speed
- Mass
- Energy
- Distance
Recall 6 vector quantities
- Velocity
- Weight
- Displacement
- Force
- Momentum
- Acceleration
magnitude in a stated directionn
What is the equation for speed?
Distance/ Time
What shows the object is stationary on a distance time graph?
speed time graph
flat line
What shows the object is stationary on a velocity time graph?
Velocity time graph
Flat line at 0
How can we calculate speed from a distance time graph?
The gradient
(draw tangent for curve)
What shows the object is slowing down on a velocity time graph ?
Velocity time graph
- Negative gradient line
- Decelerating
What shows the object is at its fastest on a distance time graph?
Distance time graph
the steepest line
What shows the object is at a constant speed on a distance time graph?
Distance time graph
straight line
How to work out the avg velocity on a velocity time graph?
- Find displacement (area under line)
- Divide by total time taken
What shows the object is returning to the start on a distance time graph?
Negative gradient
What shows the object accelerating/ decelerating on a distance time graph?
Curved line (change in speed)
What shows the object is returning/changed direction on a velocity time graph?
-line in negative y coordinates
How to calculate acceleration with speed and time?
Change in speed/ time
What is acceleration?
How much the speed/velocity changes per second. (rate of speed)
How to calculate acceleration (a) with distance?
change in velocity^2= 2 x distance x a
Describe a range of laboratory methods for determining the speed of objects
Light gates and stopwatch
1) One light gate
2) Measure length of card (shows how fast it moves across)
4) Input on data logger
5) Data logger times how long card intercepts it
Distance (card)/ Time (card intercepted)= speed
----->Use stopwatch and known distance
Avg speed of:
Walking
Runnning
Cycling
Car
Train
Plane
-1.5m/s
-3m/s
-6m/s
-13—>30m/s
-50m/s
-235m/s
Avg speed of
Sound
331.5m/s
What is the acceleration at freefall?
10m/s^2
What is Newton’s first law?
- Object at rest remains at rest
- Object in motion will remain in a constant velocity unless acted upon (as there is nothing to keep it moving faster, or stop it)
and units
What is Newton’s second law?
F=ma
- Acceleration and Force are proportional
—–> (mass is constant)
- F (N)
- M (kg) (inertial mass)
- A (m/s^2)
inertial mass
What is Newton’s third law?
- Every action has an equal but opposite reaction
firing a gun cuases backfrie
pushing a table results in me feeling force
And relationship between G and W
Weight equation?
W= M x Gravitational field strength (10)
Proportional
Core Practical: Investigate the relationship between force mass and acceleration by varying the masses added to trolleys
1) Two light gates between ramp (two differentt speeds)
2) Input distance on data logger
3) Card on trolly
4) Find trolly mass
5) Attach to pulley’s string
6) Attach (varied) mass to string on opposite end
7) Collect results mass affects speed
8) Repeat using different masses
Relationship between mass and gravitational field strenght?
Greater the mass the greater the gravitational field strength
What happens to the velocity of an object in circular motion?
Constantly changes
Why does velocity change in circular motion even when speed remains the same?
-Velocity is vector—> linear direction
- Circular motion means angul of line is always changing
thus velocity changes
Why is must there be a resultant force for an object to move in circular motion?
without a force constantly pulling it towards the centre, it would move in a linear direction
string on a yoyo, gravity
(constanttly pulled inwards, disrupting linear movement
What is the resultant force of a circular motion called?
Centripetal force
What is the direction does the resultant force of circle motion?
Towards the centre
What is inertial mass
the difficulty to change an objects velocity
F=ma (mass is constant)
What is Newtons third law?
For every action, there is an equal and opposite reaction
Example of Newtons third law?
-Firing a gun
-Backfire
What is the conservation of momentum?
When two objects collide the total momentum is conserved
What is momentum
equation
Mass x Velocity
What happens to the total momentum when two objects move towards eachother?
-One is negative
-One is positive
-Find difference
-If Ptotal is positive both objects will move to the positive direction
-If Ptotal is negative both objects will move to the negative direction
That is Ptotal before and after collision
How to work out the momentum of an explosion (stationary)
-Both add too zero
-Therefore one must be negative
Force =
with momentum
change in momentum/ Time
F=ma, F=mv/t, a=v/t
What is terminal velocity?
-Constant velocity reached
-Gravity and Air resistence are in equilibrium
Terminal velocity
6 marks
-Accelerates due to gravitational field strength of 10 n/kg
-Falls with acceleration of 10m/s^2
-As velocity inreaces
-Air resistence increases (newtons 3rd law)
-Air resistence slows object down
-Until equilibrium is reached (terminal velocity)
-If parachute/SA increased, air resistence increases further lowering velocity
How to reduce effect of a collision?
-Longer collision time
-F=change in P/t
longer time means smaller F/ less damaging
Stopping distance=
Thinking distance + Breaking distance
What increases thinking distance?
-Alcohol (depressant)
-Tiredness/health
-Reaction time
-Distractions
What decreases thinking distance?
-Stimulants (caffeine)
-Age/Health
What affects stopping distance?
-Break quality
-Road friction
-Tyre quality
-Momentum (F=ma)
-Road state
