Forces And Motion Flashcards
What is a vector quantity
A quantity that has a magnitude and a direction
E.g. force,velocity, displacement, acceleration,momentum etc
What is a scalar quantity?
A quantity that has only a magnitude but no direction
E.g. speed,distance,mass,temperature,time, etc
What is displacement?
The shortest distance between two points
Newtons 3rd law
For every force there is an equal and opposite reaction force
What is a moment
The turning effect of a force
Moment equation
M=FD
M=moment (Nm)
F= force(N)
D=Distance(m)
What is the line of action
The line along which a force acts
What is the origin of a moment called
A pivot
To increase a moment
•Increase force applied
•Increase distance the force is applied from the pivot
How many moments can be acting on an object
1 or more
How are moments described?
Due to moments being a turning force9effect) we refer to them as clockwise or anti-clockwise
What is the principle of moments
At equilibrium the sum of clockwise and anticlockwise moments are equal
What are levers
Levers are usually force multipliers which transmit turning effects of a force, we apply an input force which is outputted somewhere else
Rules of input and output forces in levers
If the input+ output forces are on different sides of the pivot like scissors they will act in diff directions but if on the same side as the pivot (such as a wheel barrow) the forces will act in the same direction
Is the output forces usually greater or smaller
Greater
Method for the principle of moments measuring and unknown weight
A
Method:
1. Place a wooden beam over the triangular
block, with the block in the centre of the
beam acting as a pivot.
2. Place or suspend the known weight on one end of the beam
3. Measure the distance from the pivot to the centre of the weight
4. Place or suspend the unknown weight on the other end of the beam and move it until the beam is perfectly balance
5. Measure the distance from the Pivot to the centre of the unknown weight
6. use this value to calculate the value of
unknown weight, using the formula
Clockwise moments=anticlockwise moments
W1d1, = W2d2
Notes about gears
•Turn in opposite directions
•If the size of the second gear is double the first the turning effect doubles
What is friction?
The force wen one object slides over another object, friction tries to stop the movement , it is a force that acts in opposition to a moving object
Side note- it is a nuisance ad it often converts kinetic energy into thermal energy
What is centre of mass?
The centre of mass of an object is the point at which an objects mass seems to be most concentrated
How to find the centre of mass of a regular object.
Draw lines of symmetry along the objet e.g from corner to corner and side to side , the point at which all the lines cross is the centre of mass
This is because the centre of mass lies along the axis of symmetry
What is stability
The tendency o an object to not topple
How to increase stability
•Increase the wideners of its base
•Ensure its centre of mass is as low as possible
Why do objects topple?
If the line of action of the weight force lies outside for the object , there will be a turning force and the object will topple
