1 FORCES + MOTION Flashcards
Unit for mass
Kilogram (kg)
Unit for distance
Metre (m)
Unit for speed
Metre/second (m/s)
Unit for acceleration
Metre/second (^2)
Unit for force
Newton (N)
Unit for time
Second (s)
Unit for gravitational field strength
Newton/kilogram (N/Kg)
Unit for moment
Newton metre (Nm)
Unit for momentum
Kilogram metre/second (Kg m/s)
Speed equation
Average speed = Distance moved / Time taken
What does the gradient represent on a distance-time graph
Speed
What is a sharp diagonal line on a distance-time graph
Constant speed
What is a flat line on a distance-time graph
Stationary
How to investigate motion with a ramp
- Measure distance of ramp with ruler
- Time from let go to down ramp with stopwatch reset at zero
- s=d/t
- Repeat and average
How to investigate motion with a ticker timer
*Attach tape to back of object and into timer
* Far apart dots = more distance per unit time
How to investigate motion with light gates
- Requires an interupter card to break beam
- S = d/t
Acceleration equation
Acceleration = change in velocity / time
Acceleration symbol equation
a = (v-u) / t
Speed symbol equation
S = d / t
What is the gradient on a velocity-time graph
Acceleration
What does a non-straight increasing line represent on a velocity-time graph
Increasing acceleration
What does a steady sloped line show on a velocity-time graph
Constant accelration/deceleration
How do you calculate the distance from a velocity-time graph
The area underneath the graph
What can forces do to objects
Change their shape, speed and direction
On a free-body diagram, what does the size of the arrow represent
The force
What does friction do to motion
Oppose it
Correlation between friction and motion
Friction opposes motion
How do you calculate the resultant force on a free body diagram
The unbalanced force
Define a scalar quantity
A quantity that has a magnitude only
Define a vector quantity
A quantity that has a magnitude and a direction
Is force a scalar or vector
Vector
Stopping distance equation
Stopping distance - thinking distance + braking distance
What affects thinking time
- Reaction time (tierdness, drugs or alcohol)
- Distraction of phone or music
- Speed of car (faster speed)
What affects braking distance
- Road conditions (ice or oil)
- Condition of brakes/tyres (affects friction that opposes motion)
- Speed of car (faster speed)
Weight equation
Weight = mass x gravitational field strength
Weight symbol equation
W = mg
Force (basic) equation
Force = mass x acceleration
Force (basic) symbol equation
F = ma
How is terminal velocity of a falling object reached
- Initially, only weight acts, causing acceleration due to gravity (there is an unbalanced force)
- Drag opposes, and so there is less unbalanced forces, so a smaller acceleration
- Drag increases as speed increases, so weight and drag are balanced
- There is no resultant force, and the forces are balanced
- Travels at a constant (terminal) velcoity, until a force is imposed
Conservation of moments equation
Total moment clockwise = total moment anitclokwise
Conservation of moments symbol equation
F1D1 = F2D2
Moments equation
Moment = force x perpendicular distance from pivot
Define a moment
The turning effect of a force
Define the centre of gravity
The point at which all weight appears to act
State Hooke’s law
Extension is directly proportional to the force applied
Extension equation
Extension = stretched length - original (equalibrium) length
How to set up a Hooke’s law experiment
Attach a spring to a clamp, next to a ruler. Add force and measure distances
Does a spring obey Hooke’s law
- Yes
- Straight line through origin
- Can recover original shape after force causing deformation has been removed
Does a spring obey Hooke’s law
- Yes
- Straight line through origin
- Can recover original shape after force causing deformation has been removed
Does a ruber band obey Hooke’s law
- No
- Non-linear relationship
- Curved line
Does a metal wire obey Hooke’s law
- Yes, until it’s elastic limit has been reached
- There it becomes permenantly deformed, and won’t return to original length when force has been removed
Does a metal wire obey Hooke’s law
- Yes, until it’s elastic limit has been reached
- There it becomes permenantly deformed, and won’t return to original length when force has been removed
Momentum equation
Momentum = mass x velocity
Momentum equation
Momentum = mass x velocity
Momentum symbol equation
P = mv
Impulse equation
Impulse = force x time
Force (momentum) equation
Force = change in momentum / time
Force (momentum) symbol equation
F = (mv -mu) / t
Conservation of momentum
Total momentum before = total momentum after
Conservation of momentum (symbol)
MaUa + MbUb = MaVa + MbVb
Conservation of momentum (symbol)
MaUa + MbUb = MaVa + MbVb
How does a safety feture prevent harm in a veichle
- Impulse = force x time
- To produce the change in momentum required to stop the car, a force needs to be applied in the opposite direction to motion
- The feture increases the time taken to stop the care, so less force is required to change momentum
- The car is safer
S in SUVAT
Distance
U in SUVAT
Initial velocity
V in SUVAT
Final velocity
A in SUVAT
Acceleration
T in SUVAT
Time
Final velocity symbol equation
V (^2) = U (^2) + 2as
Final velocity equation
Final velocity (^2) = Initial velocity (^2) + (2 x acceleration x distance)
Final velocity symbol equation (time)
V = U + at
Final velocity equation (time)
Final velocity = Initial velocity + (acceleration x time)
State Newton’s 3rd Law
If object A pushes on object B, then object B will push on object A with an equal and opposite force
