Paper 2 speed velocity and energy Flashcards
Scalars
Quantities that are fully described by a magnitude or size (or numerical value) alone
Vectors
Quantities that are full described by both a magnitude and a direction
On a distance time graph what does a diagonal line mean
It means it’s moving at a constant speed
On a distance time graph what does a horizontal line mean
It means the object has stopped
On a distance time graph what does a steeper diagonal line mean
It means the object is going faster but still at a constant speed
On a distance time graph what does a diagonal line downwards mean
It means the object is going back to the start/ reversing still at a constant speed
What is speed
How fast you are travelling and is scalar
What is velocity
Speed in a given direction and is vector
Acceleration (m/s^2) =
Change in velocity (m/s)/ time taken (s)
In a velocity time graph what does an upwards line mean
It means the object is accelerating constantly
In a velocity time graph what does horizontal line mean
It means the car has stopped accelerating and is moving at a constant velocity
In a velocity time graph what does a shallower line mean
It means the object is accelerating less but still constant
In a velocity time graph what does a downwards line mean
It means the object is slowing down/ decelerating
In a velocity time graph what does the area under the graph mean
It shows the distance travelled D=ST
What is gravity
Gravity is a field not a force. The force due to gravity on an object is its weight
What force is acting on a book at rest and what is the equal and opposite force?
Friction is acting on the book and the equal and opposite force is the reaction of the table.
What force is acting on a floating ball and what is the equal and opposite force?
The force acting is the upthrust of water and the equal and opposite force is the weight of balls
What is the resultant force
A single force that has the same effect as all the forces combined
What happens if the forces on an object are unbalanced?
The object will accelerate
What is the thinking distance
The distance the car travels during reaction time
Thinking distance increases if…
Distractions
Tired
Under influence of alcohol or drugs
Driving fast
What is the braking distance
The distance car travels while the brakes are applied
Braking distance increase if…
High mass of car Wet/icy road Gravel on road Worn down tires Faulty brakes
What is the stopping distance
Thinking distance + braking distance
Thinking distance is proportional the speed so…
If the speed doubles the thinking distance doubles
Braking distance is proportional to speed squared so…
If the speed is doubles, the braking distance is quadrupled
What is Newton’s first law of motion
An object will remain at rest or will move at a constant velocity unless there is a resultant force acting on it
What is Newton’s second law of motion
The acceleration of an object is directly proportional to the resultant force and inversely proportional to the object mass
What is Newton’s third law of motion
If object A exerts a force on object B the object B exerts a force on object A which is equal and opposite in size and direction
What do you do if the force of the two vectors are in the same direction
The add together
What do you do if the two vectors are at 90 degrees
Use Pythagoras theorem
When is it best to use the head to tail method
When the vectors are displacements because they have an obvious order
When do we use parallelogram of forces
When there are forces
What is the weight of an object
The force of gravity acting on it
What is the mass of an object
The amount of matter in it
What happens if an object falls freely
No other forces act on it so the resultant force is its own weight. Accelerates downwards at constant acceleration of 10m/s^2 called the acceleration due to gravity
What if the object falls in a fluid
The fluid drags on an object and the drag force increases with speed. The resultant force on the object is its weight minus the drag force.
Work done
When any object is moved around work will need to be done on it to get it to move
What energy does elastic store
Elastic potential energy is stored in elastic when work is done on a an object
What happens to ‘plastic’ objects when the forces deforming it are removed
The objects don’t regain its original shape
Hookes law
States that the extension of a spring is in direct proportion with the force applied to it e.g. If the force is doubled the extension is doubled (F=ke)
What does hookes law apply to
Only elastic materials
What happens if the force added on the spring is larger
It stops being elastic and doesn’t return to its original length. It has exceeded the limit of proportionality and so Hookes law no longer applies. This is known as elastic limit
What is inertial mass
A measure of how difficult it is to change the velocity of an object. defined by the ration of force over acceleration
What happens to the acceleration of an object falling in water
Acceleration decreases as it falls because drag force increases as the object speeds up so the resultant force on it decreases
