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00 - M1 Facts to memorise

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TermDefinition
What is a Vector?
Must have MAGNITUDE and DIRECTION
What is a Scalar?
Has only MAGNITUDE
On a distance/time graph, what does the gradient tell you?
speed
On a speed/time graph, what does the gradient tell you?
acceleration
On a speed/time graph what does the area under the graph tell you?
Distance covered
What is velocity?
Vector
Distance in a given direction/time taken
What is speed?
Scalar
distance/time
What is average speed?
Scalar
total distance/total time
What is average velocity?
Vector
displacement/total time taken
What are the 5 equations of motion?
  • v=u+at 
  • v2=u2+2as 
  • s=ut+at2/2 
  • s=vt-at2/2 
  • s=(u+v)t/2
What is the condition for using the 5 equations of motion?
acceleration must be constant
What is distance?
The total length that has been moved.
What is displacement?
The direct distance between start and end points
What does negative acceleration mean?
slowing down
What is negative displacement?
displacement in the opposite direction
What is acceleration due to gravity?

9.8 m/s2

ALWAYS acts downwards

A particle is thrown vertically upwards. What is its velocity at its highest point?
zero
What does equilibrium of forces mean?

horizontal forces add up to zero

vertical forces add up to zero

Is a force a vector or a scalar?
vector
How do you find the magnitude of the resultant of 2 perpendicular forces?
Pythagoras
How do you find the magnitude of the resultant of several non perpendicular forces
Find perpendicular components (ie i,j) of all forces and then use pythagoras.
How do you find the angle at which a force is acting if you know its i and j components?
tan
What is an i vector
a unit vector acting horizontally to the right
What is a unit vector
a vector that has a magnitude (ie a length) equal to 1
What is a j vector?
A unit vector acting vertically upwards
How do you find the magnitude of a vector given in the form ai + bj?

Pythagoras

√(a2+b2)

How do you find the direction of a vector given in the form ai + bj?

 

tanθ=b/a
Give 3 facts about the vector A and the vector -A
  1. They have equal magnitudes
  2. They are parallel
  3. They point in opposite directions
Give 3 facts about the vectors A and B if A=B
  • They are equal in magnitudes
  • They are parallel
  • They point in the same direction
Give 3 facts about the vectors A and 2A
  1. One is twice as long as the other
  2. They are parallel
  3. They point in the same direction
When using the formula F=ma, what does the F stand for
F is the resultant of all the forces acting upon a particle
When 2 particles are connected, how do you find their acceleration?
F=ma for the whole system, taking the direction of movement as positive.
When 2 particles are connected, how do you find the tension in the string joining them?

F=ma for one particle.

If possible, use the particle which has +T acting upon it.

How many diagrams must you draw when answering a question?
Draw a new diagram each time the information about the question changes.
What is the formula for the maximimum friction (fmax)?
fmax=μR
In which direction does friction always act?
Friction always opposes motion, so it will always act in the opposite direction to the one the particle is moving in.
If the pushing force is less than the maximum frictional force, what happens?

Nothing.

The system is stationary, v=0

f=pushing force, so equilibrium is maintained

If the pushing force is equal to the maximum frictional force, what happens?

Nothing.

The system is at its limit.

fmax=pushing force, so equilibrium is maintained.

Although often v=0, it is possible for v to be present, but it will be constant.

If the pushing force is greater than the maximum frictional force, what happens?
There is an imbalance of forces, so the particle accelerates
When a body is said to be 'on the point of slipping', what does this mean

The system is at the limit

fmax=pushing force

v is constant (often = 0)

What is a 'moment'?

The 'turning effect' which is dependent on the magnitude of the force and the distance the force is from the pivot.

Moment = force x distance

In a friction question, what does equilibrium mean?
The pushing force is less than or equal to fmax
In a moments question, what does equilibrium mean?

All clockwise moments = all anticlockwise moments

 

OR

 

The sum of all the moments = 0

What is momentum

The effect of a moving mass

 

momentum = mass x velocity

What is conservation of momentum

total momentum before = total momentum after

 

Remember to draw before and after diagrams

What are the units of momentum?
Ns
What is impulse?

Impulse = change of momentum

Impulse = mv - mu

 

ALSO

 

Momentum = Ft

 

I = Ft = mv - mu

What are the units of impulse?
Impulse is a change of momentum, so its units are the same as momentum, ie Ns
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