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Examples of vector quantities:
Velocity, displacement, acceleration, force, e.t.c.
Examples of scalar quantities
Speed, distance, temperature, mass, time, ,e.t.c.
How do you find the average speed from a distance/time graph?
Using the total distance travelled, and the total time taken:
speed = distance / time
How do you find the instantaneous speed from a distance/time graph?
Draw a tangent at any point of the line, then use it to find the a value for both distance and time, and use these in:
speed = distance / time
What is displacement?
The distance moved in a particular direction from a point.
How can displacement be found from a velocity/time graph?
By finding the area under the line.
What can tension cause objects to do?
Accelerate
Change their shape
What is the normal contact force?
The force that acts perpendicular to the point of contact of a body and the surface it's resting on.
What is friction?
A force that opposes motion due to the contact between two surfaces.
What must all free-body diagrams feature?
The body on which forces act
The direction of application of each force (direction of arrows)
The type of each force (labelled arrows)
The size of each force (length of the arrow)
What is the moment of a force?
The product of the force and the perpendicular distance of its line of action from the point/axis.
Work done by a force:
W = F x d:
One joule of work is transferred when a force of one newton causes an object to move a distance of one meter.
What is speed?
The rate of change of distance, and a scalar quantity; measured in meters per second.
What is velocity?
The rate of change of distance, and a vector quantity; measured in meters per second.
What is acceleration?
The rate of change of velocity, and a vector quantity; measured in meters per second squared.
What does a flat line on a distance/displacement time graph represent?
A stationary object.
What does a line with a constant gradient on a distance/displacement time graph represent?
An object moving at a constant speed.
What does a curved line on a distance/displacement time graph represent?
An object that is accelerating (positive gradient)/decelerating (negative gradient).
What does the gradient of the line on a speed/velocity time graph represent?
The acceleration of the object.
What does a flat line on a speed/velocity time graph represent?
An object moving at a constant velocity.
What does a line with a constant gradient on a speed/velocity time graph represent?
An object that is accelerating at a constant rate.
What does a curved line on a speed/velocity time graph represent?
An object with changing acceleration.
How can you find the maximum height reached by an object in vertical motion?
By setting the value for velocity to 0, and assuming the acceleration is due to gravity, unless stated otherwise.
How can the velocity of a falling object be investigated and found?
Using a light gate at the bottom of a ramp, start a toy car/trolley rolling down, then the velocity will be found by the light gate when it breaks the two light beams shining between the gate.
How can value for g be investigated and found?
Using an ball placed on a trapdoor a known distance from a second trapdoor, and recording the time it takes from the moment the first trapdoor is released to the moment the ball lands on the second trapdoor. Then rearrange and use S = ut + 1/2 (at*2) to find the value for acceleration/g.
What is a projectile?
An object that is thrown at an angle to the horizontal, so therefore moves in both the horizontal and vertical planes.
What must be ignored for projectile motion equations to apply?
The air resistance.
What happens to a projectile's horizontal component during flight?
Nothing, as there are no forces acting on the horizontal component; it stays the same.
What happens to an projectile's vertical component during flight?
It is affected by gravity, so will change in accordance with the value for g.
How is the total time of flight of a projectile calculated?
By finding the time taken to reach the maximum height of the projectile, then doubling it. This value can then be used to find the total distance if the velocity of the horizontal component is known.
How can the resultant component of motion of a projectile be found?
By using the horizontal and vertical components of motion in Pythagoras' theorem.
What is stopping distance?
The total distance travelled from when the driver sees the hazard requiring them to stop to when the vehicle stops; it is the sum of the thinking and braking distances.
What is thinking distance?
The total distance travelled from when the driver sees the hazard requiring them to stop to when the driver acknowledges that they must stop and applies the brakes.
What is braking distance?
The total distance travelled from when the driver applies the brakes to when the vehicle stops.
What are the factors affecting thinking distance?
Initial speed of the vehicle
The driver's reaction time (factors that affect this include: tiredness, influence of drugs and alcohol, and distractions, such as mobile devices or passengers).
What are the factors affecting braking distance?
Initial speed of the vehicle
The condition of the road (this involves poor weather conditions, such as ice or snow, as well as the quality of the road material)
The condition of the vehicle (this involves conditions of brake pads, tyres, and also the total weight of the vehicle).
How is the thinking distance related to the initial speed?
It is proportionate to the initial speed, as thinking distance is calculated by multiplying the initial speed of the vehicle by the driver's reaction time.
How is the braking distance related to the initial speed?
It is proportionate to the square of the initial speed.
What happens when a resultant force acts on an object?
The object accelerates.
What is the Newton?
A unit of force; one newton is the force that will give a mass of one Kilogram an acceleration of one meter per second squared.
What is weight?
The force of gravity that acts on an object; found by multiplying the mass of an object by the acceleration due to gravity: F = Ma.
What is tension?
The force that acts within a stretched cable or rope.
What is one-dimensional motion?
Linear motion; motion acting in a single, straight line.
What is two-dimensional motion?
The motion of an object that is moving in two dimensions, that is caused by the application of a constant resultant force.
What happens to an object experiencing a constant resultant force?
It will accelerate.
What is drag in the air?
Air resistance.
What factors affect drag?
The density of the fluid
The speed at which the object is moving (objects moving at greater speeds experience more drag)
The cross-sectional area of the object
How does drag affect a falling object?
As the object falls, its velocity increases. This in turn increases the drag force acting on the object, which causes its acceleration to decrease. This continues to occur until the drag force is equal to the object's weight, at which point it has reached a constant terminal velocity.
How can an object's terminal velocity be investigated and found?
By releasing a ball bearing from rest into a measuring cylinder full of water whilst starting a timer, then marking the position of the ball bearing after each second on the tube, we know that the ball bearing has reached its terminal velocity once the distance travelled between each interval is the same.
What is a moment?
The turning effect of a force about an axis or pivot; the magnitude of the force multiplied by the perpendicular distance from the force to the pivot, so its unit is newton meters.
What happens to the moment if its force acts on the pivot?
It will be zero, as the moment is found by multiplying the force by the distance from the pivot, so when the distance is zero the moment is zero.
What is a couple?
A pair of forces that have equal magnitude and act in opposite directions, and are applied to an object in parallel with one another. They combine to produce a rotational force about the central pivot point, rather than a translational movement.
What is the torque of a couple?
The product of the magnitude of one of the forces and the perpendicular distance separating the two forces; this is equal to the total moment of the couple.
What happens to a body's moment when it is in equilibrium?
As there is no resultant force, the moment will be zero.
What is necessary for the principle of moments to apply?
For a body to be in equilibrium, the sum of the clockwise moments at a point must equal the sum of the anticlockwise moments at that same point.
What is an object's centre of mass?
The point of an object through which all of its weight appears to act.
What happens when a resultant force is applied to an object's centre of mass?
The object will move in a straight line, with no rotational movement.
How can you use string and a ball bearing to find an object's centre of mass?
The object is suspended from a point, along with a ball bearing on a string, then the line it creates from that point is drawn onto the object
The same object is then suspended from a different point, along with the same ball bearing on a string, then the second line is drawn
The point at which the lines intersect is the centre of mass.
What is density?
The mass per unit volume of a substance; it is found by dividing an objects mass by its volume, and is represented by ρ.
How can the density of a regular object be found?
Weigh the object on a balance to find its mass
Calculate its volume by taking accurate measurements using vernier callipers, and completing various calculations
Find density using ρ = M / V.
How can the density of an irregular object be found?
Weigh the object on a balance to find its mass
Submerge the object fully in a eureka can, collect the water that is displaced by the object in a measuring cylinder, then read the volume from the scale
Find density using ρ = M / V.
What is pressure?
The normal (acts perpendicular to an objects surface) force exerted on a surface per unit cross-sectional area, measured in pascals; found by dividing the force exerted on the object by its cross-sectional area, which gives newtons per meter squared.
How does an submerged object experience pressure?
Due to the weight of the fluid above it, as the fluid particles collide with the object's surface.
Where does the pressure at the base of a cylinder of fluid act?
In all directions.
What is upthrust?
The upwards force that acts on an object when it is either partially or fully submerged in a fluid. This is because the pressure acting on the base of the object is greater than that acting on the top of it.
What is Archimedes' principle?
The upthrust exerted on a body immersed in fluid, whether partially or fully submerged, is equal to the weight of the fluid that the body displaces.
What occurs when a force is required to provide motion?
A transfer of energy occurs, the magnitude of which depends on the force required and the distance that the object moves as a result of this force. This transfer of energy is work done.
What is work done?
A transfer of energy that occurs due to the requirement of a force to provide motion; the product of the magnitude of the force and the distance moved by the object in the direction of the force.
What is the unit for work done?
Work done is measured in joules; one joule of work is done when a force of one newton moves an object one meter in the direction of the force.
What are the different forms of energy?
Kinetic energy, Gravitational potential energy, Elastic potential energy, Electric potential energy, Sound energy, Internal energy, Electromagnetic energy, Nuclear energy, and Chemical energy.
What is kinetic energy?
The energy associated with the motion of an object with mass; measured in joules, with SI base unit Kilogram Meters squared per second squared (KgM2s-2)
What is Gravitational potential energy?
The energy stored by an object at a point in a gravitational field.
What is Elastic potential energy?
The energy stored as a result of a reversible change in an object's shape.
What is Electric potential energy?
The energy of charges due to their position in an electric field.
What is Sound energy?
The energy of a mechanical wave due to the movement of atoms.
What is Internal energy?
The sum of the randomly distributed kinetic and potential energies of the molecules in a substance.
What is Electromagnetic energy?
The energy from electromagnetic waves, stored within oscillating fields.
What is Nuclear energy?
The energy stored in nuclei, released when particles in nuclei rearrange.
What is Chemical energy?
The energy contained in chemical bonds, released when atoms rearrange.
What is the principle of conservation of energy?
In a closed system, energy cannot be created or destroyed; the energy that was present before the transferal is always equal to the energy that is present after the transferal.
What is the transfer of energy equivalent to?
The work done.
What does the exchange between gravitational potential energy and kinetic energy involve on a roller coaster (in a closed system)?
As the carriage moves up a hill, the kinetic energy starts to transfer to the gravitational potential energy store, which in turn transfers back to kinetic energy once it travels back down the hill. As the maximum kinetic energy equals the maximum gravitational potential energy, we can set the two equations equal to each other, and from this we can prove that an objects mass has no bearing on its final speed, which shows that acceleration due to free fall is the same for all objects.
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