Studied by 1 person
What do vectors have? Name 2
Magnitude and direction
Velocity, displacement, force, acceleration, momentum
What is force?
When an object experiences a push or pull because of another object interacting with it.
What is an interacting pair?
Two forces that are equal and opposite and act on two interacting objects
What is gravitational force?
The force of attraction between masses
What is weight?
The force acting on an object due to gravity (the pull of the gravitational force on the object)
How can the strength of a gravitational field vary?
It’s stronger the closer you are to the mass causing the field and stronger for larger masses
What is weight dependant on?
The strength of the gravitational field where the object is. This means the weight of an object can be different on earth than on mars.
Where is weight measured from?
A single point called the centre of mass (a point at which you assume the whole mass is concentrated) for a uniform shape (same density throughout) this is at the centre of the object
What is the difference between weight and mass?
Mass is not a force and is measured in Kg weight is a force and is measured in N
What is the relationship between mass and weight?
They are directly proportional
What is the resultant force?
All the forces acting on the same line added together, this is the overall effect of the forces
How can work be done in relation to resultant forces?
When a force moves an object through a distance work is done and energy is transferred. This can be done usefully or wasted. Work done and energy transferred are the same.
How does a force move an object?
A force needs to be applied, this force needs energy such as fuel or food. The force does work to move the object and energy is transferred from one store into another.
How can you find out how much work has been done?
Work done = force x distance
One joule of work is done when a force of one newton moves and object one meter
How to use a scale drawing to find resultant forces
Draw all the forces acting on the object.
Draw a line from the start of the first force to the end of the second force.
The angle measures the direction (as a bearing) and the length of the line measures the magnitude of the resultant force.
What does it mean if an object is in equilibrium?
The forces acting on it combine to give a resultant force of 0
What can you do if a force is acting at an awkward angle? (When trying to measure)
Split it into components usually horizontal and vertical using grid paper
What happens in terms of energy stores when an object is stretched/compressed?
Work is done which causes energy to be transferred to the objects elastic potential energy stores
What happens when an object is said to be elastically deformed? In terms of energy stores
All of this energy is transferred to the elastic potential energy stores of the object
What is the difference between elastic deformation and inelastic deformation?
When something is elastically deformed it can return back to its original shape however when it’s inelastically deformed it can’t. Only elastic objects can be elastically deformed
What’s the relationship between extension and force?
They are directly proportional
F=ke
What is the limit of proportionality? And how do we see it on a graph?
The limit to the amount of force you can apply to an object before the extension stops increasing proportionally.
It is shown as a curve in the graph
How to investigate the link between force and extension?
Before starting the experiment, measure your masses using a mass balance the use W=mg to calculate their weight.
You can conduct a pilot study to check your masses are an appropriate size for your experiment. Using a spring identical to the spring you will use in the investigation, add your masses one by one measuring the extension each time if you add a mass and the spring increases more than the last time you have reached the spring’s limit of proportionality and you should use smaller masses.
Measure the natural length of the spring with a millimetre ruler attached to a clamp, take the reading at eye level and use a thin strip of tape to the ruler where the bottom of the spring is yon make the reading more accurate.
Add the mass to the spring and allow the spring to come to rest record the mass and measure the new length of the spring. The extension is the change in length.
Repeat the process at least 6 times.
How to plot results for the practical? And what the lines mean?
If the line of best fit is straight there is a linear relationship between force and extension (directly proportional)
The gradient of the straight line is the spring constant
When the line begins to bend the relationship is now nonlinear- the spring stretches more per unit in force
The area under the line is the energy stored in the springs elastic potential energy store
What is a moment?
The turning effect of a force
What effects the size of a moment?
To get the maximum moment you need to do work at right angles (perpendicular) to the pivot.
A larger or smaller distance
A larger or smaller force
How to find a missing force or distance in a moment question?
If the total anticlockwise moment equals the total clockwise movement about a pivot, the object is balance and won’t turn
How do gears work?
They are circular disks with teeth
There teeth lock (with another gear) so that turning on causes another to turn in the opposite direction
What do gears do?
Transmit rotational force from one place to another
What can different sized gears be used for?
To the change the moment of the force, a force transmitted to a larger gear will cause a bigger moment as the distance to the pivot is greater
How do particles exert pressure?
They have mass and exert a force on the object they collide with. Pressure is force per unit area
Why does the pressure of a liquid increase with depth?
As the depth of a liquid increases, the number of particles above that point increases, the weight of these particles adds to the pressure felt at that point.
Why does the density of a liquid increase the pressure of the particles in that liquid?
The more dense a liquid is, the more particles it has in a given space, this means more particles are able to collide so the pressure is higher.
Which direction is the pressure of a fluid exerted?
Normal (at right angles) to the surface
Why do objects submerged in fluids experience upthrust?
When an object is submerged in water (fully or partially) the pressure of the fluid is exerted from every direction
Pressure increases with depth, so the force on the bottom of the object is larger than the top
This causes a resultant force upwards, known as upthrust
The upthrust is equal to the weight of fluid that has been displaced by the object
What would make an object sink in a liquid?
If an object weight is more than the upthrust it sinks as it is denser than the fluid it’s placed in so is unable to displace enough liquid to equal its weight.
What would make an object float in a liquid?
If the upthrust of an object is equal to (or less than) the objects weight, it floats as it is able to displace enough liquid to equal its weight, so the upthrust is equal to its weight before it is completely.
How is atmospheric pressure created?
It’s created in a surface by air molecules colliding with the surface
Why does atmospheric pressure decrease as height increases?
As the altitude increases, the atmosphere gets less dense so there are fewer air molecules that are able to collide with the surface. There are also fewer air molecules above a surface as the height increases. This means that the weight of the air above it which contributes to atmospheric pressure, decreases with altitude.
What is the difference between distance and displacement?
Distance is scalar, Displacement is a vector
What are the typical speeds for walking, running and cycling?
Walking- 1.5 m/s
Running- 3 m/s
Cycling- 6 m/s
What are the typical speeds for a car, a train and a plane?
A car- 25 m/s
A train- 55 m/s
A plane- 250 m/s
What is acceleration?
The change in velocity in a certain amount of time
Change in velocity (m/s) ÷ time (s) = acceleration (m/s²)
What is the acceleration due to gravity for objects in free fall?
9.8 (m/s)
In a calculation how would you quantify deceleration?
Put a minus in front of the velocity
In a distance time graph what do these mean; Gradient, flat sections, straight uphill sections, curves, a steepening curve and a cure that is levelling off?
Gradient = speed
flat sections- object is stationary
straight uphill sections- travelling at a steady speed
curves- acceleration or deceleration
a steepening curve- object is speeding up
a curve that is levelling off- slowing down
How to find the speed of an object on a distance time graph at a changing speed?
Finding the gradient of thentangent to the curve at the point you need
What do these mean on a velocity time graph; Gradient, Flat sections, a steeper section, Uphill/downhill sections and the area under the graph?
Gradient = acceleration
Flat sections- travelling at a steady speed
A steeper section- greater acceleration/deceleration
Uphill/downhill sections- acceleration and deceleration
Area- the distance travelled
What is drag?
The resistance you get in a fluid (gas or liquid). The frictional force produced by air acting on a moving object.
Where does friction occur?
Between two surfaces in contact or when an object passes through a fluid (drag)
How are drag and speed related?
Drag increases with speed
Why do objects falling through fluid reach terminal velocity?
At first gravity is much more than the frictional force slowing them down so the accelerate
As speed increases friction builds up
This gradually reduces the acceleration until the frictional force is equal to the accelerating force (so the resultant force is zero)
It will have reached its maximum speed or terminal velocity and will fall at a steady speed
What’s an example of when speed will be constant with a changing velocity?
An object moving in a circle, eg a car going around a roundabout
Note 
Flashcard (20)