Science Term 2 Exam- Physics Flashcards
Whats the difference between speed and velocity
Speed is how fast something is going
Velocity is how fast something is going in a certain direction. Negative and positive numbers are used
How to: Distance time graphs
Horizontal axis (x axis) is for time
Vertical axis (y axis) is for distance
Your graph must have a title, labelled axis with units, the scale must be even
The gradient (slope) of the line tells us the speed of the object
If it has a positive gradient means it has a positive speed
If it has a negative gradient means it has a negative speed
Units
1km = 1000 meters 1m = 100 cm 1cm = 10mm
Distance, time and velocity
To find velocity/speed- d / t
To find distance- v x t
To find time- d / v
What are ways to unit speed
Km/h Kmh-1 = m / s
M/s Ms-1 = k / h
Ms-1 to Kmh-1 = Ms-1 x 3.6
Kmh-1 to Ms-1= Kmh-1 / 3.6
What is a force?
A force is a push or pull that can change an objects shape, size, and velocity
What is the difference between contact forces and non contact forces?
Contact forces are when objects are touching and non contact forces are when there is no physical touching (eg gravity)
How do you measure force
Units for force is Newton (N)
1N is the amount of force needed to accelerate 1kg at 1ms-2 (Units for acceleration is ms-2 or m/s/s)
Types of forces
Gravity Air resistance Support Uplift Friction Thrust Buoyancy
Force diagrams
We use arrows to represent forces
Sometimes the size of the arrow represents the size of the force
Sometimes the forces are too different and we just write the value
If forces are in the same direction you add the amounts to get the net force
But if they are in opposite directions you subtract
Newtons first law of motion
An object that is at rest will stay at rest unless acted on by a outside force
An object in motion will stay in motion
Balanced and unbalanced forces
When forces are balanced we can say they are equilibrium
When they are unbalanced they have a net force
Balanced eg. 2N to the left and 2N to the right
Unbalanced eg. 4N to the left and 1N to the right
What is a net force?
The sum of all the forces is a Net Force
Newtons 3rd Law
For every force there is a equal opposite reaction of force
Eg. Standing on the ground, balance game, stepping off a boat, kicking a ball
Non contact forces
Gravity
Magnetism
Electricity
What is gravity?
Gravity is the attraction between 2 masses
The closer the masses the greater the attraction
The further apart the masses the weaker the attraction
The larger the mass the greater the attraction
The smaller the mass the smaller the attraction
Mass V Weight
Mass is the amount of matter/stuff/quantity of material that makes you, it doesnt change
Weight is the gravitational pull on your mass
W= mass x force of gravity = mg
Measured in Newtons
Eg. w= 75 x 10 = 75N
Weightless in space
The person and the space craft are falling at the same rate and since they are falling at the same rate there is no observational reaction force
Acceleration
Acceleration is a change in motion (velocity) of a object
Forces cause acceleration
It is measured in metres per second per second
Acceleration= (Final speed - Initial speed) / time
A= Vf - Vi / T
A triangle means a change in
Working out acceleration time and velocity
A= Change in velocity / Time
T= Change in velocity / Acceleration
Change in velocity= Acceleration x Time
