Forces Flashcards
what is a scalar quantity?
it has magnitude(size) only e.g the number of apples
what is a vector quantity?
it has magnitude(size) and direction e.g velocity.
what is the velocity of something?
it shows the speed and the direction of travel
in vector quantities what can the length of an arrow represent?
it shows the magnitude
in vector quantities what can the direction of the arrow represent?
the arrow points in the direction that the vector quantity is acting
what is an example of a vector quantity?
forces
when does a force occur?
when two or more objects interact
forces are either…
contact or non- contact forces
what is a contact force?
when the objects are actually touching.
what are examples of contact forces?
friction, air-resistance/drag, tension, normal contact force, upthrust
what is a non-contact force?
when the two objects are not touching.
what are examples of non-contact forces?
gravitational force, electrostatic force, magnetic force
what is friction?
The resistance that one surface or object encounters when moving over or through another material. Friction generally causes heat.
what is air- resistance/drag?
the force acting on an object that is moving through air flowing in the opposite direction. The air “resists” the object’s movement, slowing it down by friction that is created as the object collides with air molecules.
what is tension?
the pulling force that a string or cable exerts (creates) when something or someone pulls on it.
what is upthrust?
a force that pushes up on an object submerged in a fluid It is always in the opposite direction to the object’s weight.
what is gravitational force?
objects have a force pulling them down due to their mass. The gravitational field is responsible for the force of gravity close to Earth. Around the earth, there is a gravitational field which pulls objects down.
what is electrostatic force?
Two objects with the same type of charge will repel, whilst two oppositely charged objects attract. The force between unlike charges is called electrostatic attraction.
what is magnetic force?
an attraction or repulsion that arises between electrically charged particles because of their motion.
what is gravity ?
a force of attraction between all masses.
what is the force of gravity close to the earth due to?
the gravitational field around the planet
what is the mass of an object?
it relates to the amount of matter it contains and is constant
what is the force acting upon an object due to gravity?
weight.
what does the weight of an object depend on?
the gravitational field strength, where the object is and its always directly proportional to its mass.
the weight of an object is always directly proportional to what?
its mass
what is a resultant force ?
when more than one force acts on an object, these forces can be seen as a single force that has the same effect as all the forces acting together.
what are scale vector diagrams used to illustrate?
the overall effect when more than one force acts upon an object, the forces are added together to find a single resultant force, including magnitude and direction. the vectors are added head to tail and a resultant force arrow is drawn.
when can scalar vector diagrams also be used?
when a force is acting in a diagonal direction, expressing the diagonal force as two forces at right angles to each other can help work out what effect the force will have
what can force Fr be broken down into?
F1 and F2, F1 is the same length as the length of Fr in the horizontal direction and F2 is the same length as Fr in the vertical direction.
how do you find Fr?
Fr = F1+F2
what are the measurements of the aspects in the equation: Weight = mass x gravitational field strength?
weight is measured in newtons
mass is measured in kg
gravitational field strength is measured in newtons per kg
what happens when a force causes an object to move? why?
work is done on the object, because it requires energy to move the object.
1 joule = __ newton metres?
1 newton metre, one joule of work is done when a force of one newton causes a displacement of one metre.
what is the definition of displacement?
the change in position or placement of an object
what are the measurements of the aspects in the equation: work done = force x distance
work done is measured in joules
force is measured in newtons
distance is measured in metres
what happens when work is done ?
energy transfers take place within the system
what are examples of work being done?
- work done to overcome friction = causes an increase in heat energy
- an electric lift uses electrical energy to do work against gravity= this leads to an increase in gravitational potential energy.
to change the shape of an object what must occur?
more than one force must be applied e.g a spring must be pulled from both ends to stretch it
what is ment by the term “ elastically deformed”?
when the object returns to its original shape after the forces are removed.
what is ment by the term “inelastically deformed”?
when the object does not return to its original shape after the forces are removed.
what is the extension of an object?
the difference between the original length and the new, longer length.
what is the extension of an elastic object directly proportional to ?
the applied force i.e they have a linear relationship and produce a straight line on a force- extension graph
Once the limit of proportionality has been exceeded what happens?
- doubling the force will no longer exactly double the extension
-the relationship becomes non-linear
-a force-extension graph will stop being a straight line
on a force- extension graph, what is the gradient of the linear section of the graph equal to ?
the spring constant (k)
on a force-extension graph, what is the area of the triangle below the graph equal to ?
work done to stretch or compress the spring
what does the spring constant indicate?
how easy it is to stretch or compress a spring- the higher the spring constant, the stiffer the spring
a force that stretches or compresses a spring stores ______ potential energy in the spring?
elastic
what is the amount of work done equal to ?
the energy stored, the spring does not go past the limit of proportionality
how do you calculate the spring constant of something?
1- calculate the extension which is the ending length - the starting length (if you do not already have it)
2- convert the extension to metres if needed
3- substitute values in spring constant equation : spring constant = force/extension
what is the method for investigating the relationship between force and extension for a spring?
1- set up the equipment
2- add 100g (1N) to the mass holder
3- measure the extension of the spring and record the result
4- repeat steps 2 to 3 times for a range of masses from 1N to 10N
what are considerations, mistakes and errors of investigating the relationship between force and extension for a spring?
- the extension is the total increase in length from the original unloaded length. it is not the total length of the increase each time.
-adding too many masses can stretch the spring too far which means repeat measurements can not be made.
what are the variables to the experiment of investigating the relationship between force and extension for a spring?
independent(deliberately changing)- the force on the spring
dependent(one that is measured)- the extension
what are hazards and risks to the experiment of investigating the relationship between force and extension for a spring?
- masses falling on feet, to prevent this keep the masses to the minimum needed for a good range of results
is distance scalar or vector?
scalar, it is how far an object moves, it does not take into account the direction an object is travelling in or even if it ends up back where it started.
is displacement scalar or vector?
vector, it has a magnitude which describes how far the object has travelled from the origin, measured in a straight line, it has a direction which is the direction of the straight line.
is speed scalar or vector?
scalar, measured in m/s, the speed that a person can walk, run or cycle depends on factors like age, fitness, environment and distance.
what are the measurements of the aspects in the equation: distance travelled = speed x time
distance= metres
speed= m/s
time= seconds
is velocity scalar or vector?
vector, it is the speed of an object in a given direction
what is an example of velocity?
when travelling in a straight line an object with constant speed also has constant velocity.
if an object is travelling in a straight line what happens to the speed and velocity?
the speed can still be constant but the velocity will change because the direction has changed.
if an object is moving in a circle what happens to the speed and velocity ?
it is accelerating even if its travelling at a constant speed and is constantly changing direction so is constantly changing velocity.
e.g orbiting planets are an example of this, it is the force of gravity that causes the acceleration.
what is newtons first law?
an object will remain in the same state of motion unless acted on by external force.
what happens when the resultant force acting on an object is zero?
-if the object is stationary it remains stationary
- if the object is moving it continues to move at the same speed in the same direction i.e at a constant velocity.
what is inertia?
the tendency (likeliness) for objects to continue in the same state of motion.
when does the velocity of an object change?
if there is a resultant force acting on it
what is a distance-time graph used to represent?
the motion of an object travelling in a straight line
on a D-T graph, where is the speed of the object found?
the speed is the gradient of the (slope) line.
on a D-T graph if the object is accelerating what happens to the line on the graph?
it will be a curve
for an accelerating object what is its speed at a particular time found by?
to find the speed at a particular time you draw a tangent to the curve at the point in time, then work out the gradient of the tangent.
what’s the acceleration of an object?
the acceleration of an object is a measure of how quickly it speeds up or slows down or changes direction.
when an object slows down what happens to the velocity?
when an object slows down, the change in velocity is negative so it has a negative acceleration.
what can the gradient of a velocity-time graph be used to find?
the acceleration of an object
in a velocity-time graph, how do you find the total distance travelled?
work out the area of the shape under the graph
what does newtons second law state?
the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object.
according to newtons second law, what happens to the acceleration if the force is doubled?
the acceleration will also be doubled
according to newtons second law, what happens to the acceleration when the mass is doubled.
the acceleration will be halved
mass is a measure of ___?
inertia, it describes how difficult it is to change the velocity of an object
according to inertia, the larger the ____ the bigger the _____ needed to change the velocity.
mass, force
what is the method of investigating the effect of varying the force and/or the mass on the acceleration of an object?
1- set up equipment
2-release the trolley and use stopwatch to take the measurements needed to calculate acceleration
3-move 100g (1N) from the trolley on to the mass holder
4- repeat steps 2 to 3 times until all the masses have been removed from the trolley onto the mass holder.
if investigating the mass, keep the force constant by removing a mass from the trolley but not adding it to the holder
what are considerations, mistakes and errors possible in the method of investigating the effect of varying the force and/or the mass on the acceleration of an object?
-when changing the force it is important to keep the mass of the system constant. masses are taken from the trolley to the holder, no extra masses are added.
- fast events often result in timing errors, repeating results and finding a mean can help reduce the effect of these errors.
- if the accelerating force is too low or the mass is too high, then the frictional effects will cause the results to be innacurate.
what are the variables for the method of investigating the effect of varying the force and/or the mass on the acceleration of an object?
independent- force or the mass
control(kept the same)- the force if the mass is changed (the independent variable) or the mass if the force is changed(the independent variable).
what are hazards and risks to the method of investigating the effect of varying the force and/or the mass on the acceleration of an object?
- masses falling on feet to minimise this, masses should be kept to the minimum needed for a good range of results.
what happens when an object falls through a fluid?
- at first the object accelerates due to the force of gravity
- as it speeds up, the resistive forces increase
- the resultant force reaches zero when the the resistive forces balance the force of gravity. at this point the object will fall at a steady speed , called its terminal velocity.
what is terminal velocity?
steady speed achieved by an object freely falling through a gas or liquid.
what does newtons third law state?
for every action there is an equal and opposite reaction, this means that whenever one object exerts a force on another, the object exerts a force back, this reaction force is of the same type and is equal in size but opposite in direction. e.g a rocket pushes fuel backwards which in turn pushes the rocket forwards.
what is momentum?
All objects have momentum,
