P5 - Forces Flashcards
What do you vector quantities have
They had a magnitude and direction
What are some examples of vector quantities
Force, velocity, displacement, acceleration
What do you scaler quantities have
I only have a magnitude and no direction
What are some examples of scaler quantities
Speed, distance, mass, time, temperature
What is the meaning of a contact force
Went to objects have to be touching for a force to act
What are some examples of a contact forces
Air resistance, tension in ropes
What’s the meaning of a non-contact force
If the two objects do not need to be touched for the force to act
What are some examples of noncontact forces
Magnetic force, gravitational force, electrostatic forces
What is the meaning of an interaction pair
Is a pair of forces that are equal and opposite and act on 2 interacting objects
What is gravitational forces
Gravity attracts all messes but you only noticed it when one of the message is really really big
What’s the effect of gravity
On the surface of the planet it makes all things fall towards the ground
It gives everything a weight
What is mass
It’s just the amount of “stuff “in an object. For any given object this will have the same value everywhere in the universe
What is weight
Is the force acting on an object due to gravity close to earth this force is caused by the gravitational field around the Earth
Where is the gravitational field strength strongest
Gravitational field strength varies with location. It’s stronger the closer you are to the mass causing the field and stronger for larger masses
What does weight depend on
It depends on the strength of the gravitational field at the location of the object. This means the weight of an object changes with its location
How do you measure weight
Using a newtonmetre
How is mass measured
Mass is not a force
Using a scale
What is a free body diagram
A diagram that shows all the forces acting on an object
What is the resistance Force
In real situations there are at least two forces acting on an object along any direction
If you have a number of forces acting at a single point you can replace them with a single force
The single force is called the resistant force
How do you workout resistant force
Considered the horizontal and vertical direction separately
Subtract The horizontal size
Subtract the vertical size
State the size and direction of the resistant force
How is a resistant force moving an object doing work on it
To make something move a force must be applied
The thing applying the force needs a source of energy
The force does “work “to move the object and energy is transferred from one store to another
With the energy is transferred “usefully “or is “wasted”you can still say that “work is done “
What is special about mass and weight
They are directly proportional
How do you use a scale drawing to find resistant force
Start by flooring a scale drawing of the forces acting
Make sure you choose a sensible scale
For the resistance from the tale of the first arrow to the tip of the last Arrow (draw the hypotenuse)
Measured the hypotenuse and use the scale to find the force in newtons
Use a protractor to measure the direction as a bearing
What is equilibrium
If all of the forces acting on an object combined to give a resistant force of zero the object is in equilibrium
How do you draw a scale diagram of an object in equilibrium
On a scale drawing this means that the tip of the last force you drew food and where the tip of the first force you to began
You might be given forces acting on an object and told to find a missing force given that the object is an equilibrium. To do this Draw out the forces you to know, join the end of the last force to the Start of the first force. This line is the missing Force so you can measure its size and direction
How do you work out the force acting on something at an awkward angle
Split it into two components-vertical and horizontal component
Draw them using a sensible scale
Work out the hypotenuse using the scale factor
How does stretching, compressing and bending transfer energy
When you apply a force to an object you may cause it to stretch ,compress or bend
To do this you need more than one force acting on the object
An object has been elastically deformed if it can go back to its original shape and length after the force has been removed
Objects that can be electrically deformed are called elastic objects
An object has been inelastically deformed it doesn’t return to its original shape and length after the force has been removed
Work is done when a force stretches or compresses an object and causes energy to be transferred to the elastic potential energy store of the object
All of the energy is transferred to the elastic potential energy store if it is elastically deformed
What is the relationship between extension and force
Extension of a spring is directly proportional to the load or force applied
How do you use F = KE to work at compression
Where he is just the difference between the neutral and compressed length-the compression
What happens to an elastic object when there is too much force
There is a limit to the amount of force you can apply to an object for the extension to keep on increasing Proportionally
The object will not return to its original shape and length
What’s the difference between speed and velocity
Speed and velocity both mega how fast you’re going what speed is a scaler and velocity is a vector
This means you can have objects travelling at a constant speed with a change in velocity. This happens when the object is changing direction whilst playing at the same speed.
If you want to measure the speed of an object that’s moving with a constant speed you should time how long it takes to object to travel a certain distance
Objects rarely travel at a constant speed
What’s the meaning of speed
Speed is just how fast you’re going with no regards to the direction
What’s the meaning of velocity
Velocity is speed in a given direction
What’s the typical speed of
A person walking
A person running
A person cycling
A train
A car
A plane
1.5 m/s
3 m/s
6 m/s
30 m/s
25 m/s
250 m/s
What’s the speed of sound in air
330 m/s
What does the speed of sound changing depend on
It depends on what the sound waves are travelling through and the speed of wind is affected by many factors
Windspeed can be affected by things like temperature, atmospheric pressure and if there are any large buildings or structures nearby
What’s the meaning of acceleration
Is how quickly your speeding up
acceleration is the change in velocity in a certain amount of time
Deceleration is just negative acceleration
How do you estimate acceleration
To do this you need the typical speed of the object
What is uniform acceleration
Constant acceleration is sometimes called uniform acceleration
acceleration due to gravity is uniform for objects in freefall. It’s roughly equal to 9.8 m/s
What does distance time graph’s show us
Gradient = speed (The steeper the graph the faster it’s going) = Y axis divided by X axis
Flat sections are where it’s stationary-it’s stopped
Straight uphill sections mean it’s travelling at a steady speed
Curves represent Acceleration or deceleration
A steeper curve means it’s speeding up
A levelling off curve means it’s slowing down
If the object is changing speed you can find its speed at a point by finding the gradient of the tangent to the curve at that point
What does a velocity time graph shows
Gradient - acceleration
Flat sections represent travelling at a steady speed
The steeper the graph the greater the acceleration or deceleration
Uphill sections are acceleration
Downhill sections or deceleration is
The area underneath any section of the graph is equal to the distance travelled in that time interval
What does fiction do
If any object has no force propelling it along it will always slow down and stop because of fiction
Fiction always acts in the opposite direction to the mental
To travel at a steady speed the driving forces needs to balance the frictional forces
You get friction between two surfaces in contact or when the object passes through a fluid
You can reduce friction between services by using a lubricant
How does drag increasing also increase speed
Drag is the resistance you get in fluid. Air resistance is a type of drag
An important factor by far in reducing drug is keeping the shape of the object streamlined
This is where the object is designed to allow fluid to flow easily across it reducing drag.
Frictional forces from fluids always increases with speed
What is terminal velocity
When a falling object 1st sets off the force of gravity is much more than the frictional force slowing it down so it accelerates
As the speed increases the friction builds up
This gradually reduces the acceleration until eventually the frictional force is equal to the acceleration force so the resultant force is zero
It will have reached the maximum speed or terminal velocity and will fall at a steady speed
What does terminal velocity depend on
Typically the Less streamline an object is the lower its terminal velocity
So objects with large surface area tend to have low terminal velocity
Shape
What is Newton’s first law
If the resultant force on a stationary object is zero the object will remain stationary. If the resultant force on a moving object is zero it’ll just carry on moving in the same velocity (same speed and direction)
What’s the relationship between acceleration, resistant force and mass
The launch of the resisting force acting on an object the more the object accelerates-the force and the acceleration Is directly proportional
Exhilaration is also inversely proportional to the mass of the object-so an object with a larger mass will accelerate less than one with a smaller mass
What is Inertia
Until acted upon by A resultant force object at rest day stay at rest and objects moveing at a steady speed will stay moving at that speed. This tendency to continue in the same state of motion is called inertia
And objects inertia mass measures how difficult it is to change the velocity of an object
What is Newton’s third law
When two objects interact the forces they exert on each other are equal and opposite
What is stopping distance
The distance it takes to stop a car in an emergency
What is the thinking distance
Thinking distance is how far the car travels during the drivers reaction time (the time between the drivers seeing a hazard and applying the brakes)
What is the braking distance
Braking distance is the distance taken to stop under the braking force (once the brakes are applied)
What is the thinking distance affected by
If you’ve had alcohol or drugs
Age
What is braking distance affected by
Your speed-for a given braking force the faster vehicle travels the longer it takes to stop
The weather or road surface-if it is wet or icy or there are leaves or are you on the road there is less grip between the vehicles tires and the road which can cause tires to skid
Conditions of your tires-if the tires of a vehicle haven’t got any presents left then they cannot get rid of water in wet conditions. This leads to them skidding on top of water
How good your brakes are-if brakes are worn or faulty they won’t be able to apply as much force as well maintained breaks which can be dangerous when you need to break hard
How does breaking occur
When the brake pedal is pressed this causes brake pads to be pressed onto the wheel. This contact causes friction which causes work to be done.Transfers energy from the kinetic energy store of the wheel to the thermal energy store of the breaks. The break increases in temperature
The faster a vehicle is going the more kinetic energy it has and so more work needs to be done to stop at. This means that a greater braking force is needed to make it stop within a certain distance
A large braking force means a larger deceleration. Very large deceleration can be dangerous because they may cause breaks to overheat or could cause the vehicle to skin
What is momentum
The greater the mass of an object or the greater its velocity the more momentum the object has
Momentum is a Vector quantity
What is the conservation of momentum
In a closed system the total momentum before an event is the same as after the event
If the momentum before and event is zero then the momentum after will also be zero
