Forces and Motion Flashcards
Unit of mass
Kilograms (kg)
Unit of distance
Meters (m)
Unit of speed
Metres/ seconds (m/s)
Unit of acceleration
Metres/ seconds^2 (m/s^2)
Unit of force
Newton (N)
Unit of time
Seconds (s)
Unit of Gravitational Field Strength (GFS)
Newtons/ kilogram (N/kg)
Unit of momentum
Kilogram metres/ second (kg m/s)
How to calculate the speed from a distance-time graph?
Find the gradient =
Change in y / Change in x
What is the equation for Speed?
Speed (m/s) = Distance (m) / Time (s)
What is the equation for Acceleration?
Acceleration (m/s^2) = Change in Velocity (m/s) / Time taken (s)
How do you calculate the distance moved from a velocity-time graph?
Calculate the area under the graph
How to calculate acceleration in a velocity-time graph?
Find the gradient =
Change in y / Change in x
How to calculate Final Speed using final speed, initial speed, acceleration and distance moved?
v^2 = u^2 + 2as
(final speed)^2 = (initial speed)^2 + (2 x acceleration x distance moved)
What is a scalar quantity?
A quantity that only has magnitude (eg. mass, kg)
What is a vector quantity?
A quantity that has direction and magnitude (eg. force, velocity)
What is a resultant force?
The sum of the total forces acting on an object.
What is the equation that links Force, Mass and Acceleration?
F = ma
F = Force (N)
m = Mass (kg)
a = Acceleration (m/s^2)
What is the equation that links weight, mass and Gravitational Field Strength?
W = mg
W = Weight (N)
m = Mass (kg)
g = Gravitational Field Strength (N/kg)
What is the equation for stopping distance?
Stopping Distance = Thinking distance + Braking distance
What are some factors affecting the stopping distance?
- Speed
- Mass
- Incline of road
- Impairment due to alcohol/drugs
- Condition of braking system
- Condition of road
What is terminal velocity?
When the force of Weight downwards is the same as air resistance upwards and so the object moves at a constant velocity, with no overall force.
What is the Hooke’s Law equation?
F = ke
F = Force (N)
k = Spring constant (N/M)
e = Extension (m)
What is Hooke’s Law
Hooke’s Law states that the extension of a spring is directly proportional to the applied force, up to the limit of proportionality.
What is an elastic?
A material that returns to its original shape after the forces causing deformation have been removed.
What is the momentum equation?
p = m x v
p = Momentum (kg m/s)
m = Mass (kg)
v = Velocity (m/s)
Describe using the idea of momentum how airbags work as a safety feature?
- Airbags inflate quickly during a crash, preventing a passenger’s head from hitting hard objects.
- Increases the amount of time it takes for the momentum of the person’s head to reach 0, reducing the rate of change.
- F = mv-mu/t, so increasing t reduces F.
Describe using the idea of momentum how seatbelts work as a safety feature?
- They prevent someone being thrown out of a car during a crash.
- Seatbelts can stretch slightly, increasing the time taken for a person’s body to stop moving, reducing the rate of change of momentum.
- Since F = ma, reducing, a reduces F.
Describe using the idea of momentum how crumple zones work as a safety feature?
- Crumple zones are areas of a vehicle that are designed to give way during a crash.
- By doing so, they increase the time taken for the car to come to a stop, decreasing the rate of change.
- Since F = ma, decreasing a decreases F.
What is The Principle of the Conservation of Momentum
Momentum before = Momentum after
What is the equation that links Force, Change in momentum and time taken.
F = (mv - mu) / t
F = Force (N)
mv = Final momentum (kg m/s)
mu = Initial momentum (kg m/s)
t = Time (s)
What is Newton’s First Law
An object will remain stationary or travel at constant velocity unless an external resultant force is applied.
What is Newton’s Second Law?
The acceleration of an object is directly proportional to the resultant force applied to the object.
F = ma
Also:
F = (mv - mu) / t
Force is the rate of change of momentum
What is Newton’s Third Law?
If Object A imparts a force on Object B, Object B imparts an equal and opposite force on Object A.
What is the equation for Moments?
M = fd
M = Moment (Nm)
f = Force (N)
d = Perpendicular distance to pivot (m)
Explain this practical: Investigate how extension varies with applied force for helical springs, metal wires and rubber bands.
Set up a clamp with a weighted stand and a spring with hanging masses
Measure length of spring when no load is applied
Apply one mass and measure length of spring when it comes to a rest
Repeat this and plot a graph of force vs total extension
How does the weight of body acts with gravity?
It acts through its centre of gravity
Explain the direction and how weight works as a force:
The result of your own mass being pulled down by a gravitational field
Downwards
Explain the direction and how driving force/ thrust works as a force:
A force that moves a mechanical object
Fowards
Explain the direction and how resistive forces works as a force:
Name given to all forces that try to slow down an object
Backwards
Explain the direction and how air resistance works as a force:
A force from air that slows down moving objects
Backwards
Explain the direction and how braking force works as a force:
A force deliberately applied to slow down a mechanical object
Backwards
Explain the direction and how friction works as a force:
Force from solids rubbing together (slows object and produces heat)
Backwards
Explain the direction and how upthrust works as a force:
A force from a fluid which helps keep planes in air
Upwards
Explain the direction and how reaction force works as a force:
A force pushing away from and object at 90°, reacting to the force pushing against it
Away from surface
Explain the direction and how electrostatic force works as a force:
A force between electrically charged objects
Towards/ away from electric charge
Explain the direction and how gravitational force works as a force:
An attractive force between any two masses arising from a gravitational field between any two masses
Explain the direction and how magnetic force works as a force:
A force coming from a magnetic field
Towards/ away from magnet
Explain the direction and how tension works as a force:
A pull force acting in a rope, spring or piece of spring
Along the object, away from object acting on it
