Mechenics Flashcards
(35 cards)
what’s a scalar and vector
a scalar has no direction it’s just the amount of smth
ex. mass, temp, time, speed
a vector has magnitude and direction
ex. displacement, velocity, force, acceleration
what’s a moment and what’s formula
a turning effect of a force
M=Fd
force x perpendicular distance from the point to the line of action of force
what is equilibrium
the sun of the clockwise moments bout any point equals the sum of the anti-clockwise moments about the same point
what’s a couple
a pair of forces of equal size which act parallel to each other but in opposite directions
it doesn’t produce a turning effect
what does inertia mean
any mass has a resistance to a change in velocity when subjected to a force
what is centre of mass
it’s the single point that you can consider it’s whole weight to act through
how do you get the centre of mass of an irregular object
- hang the object freely from a point
- draw vertical line downwards from the point of suspension
- hang the object from a diff point
- draw anotherr vertical line downwards
- center of mass is where the two lines cross
how does an object topple over
if the vertical line drawn downwards from its centre of mass falls outside its base area
this happens because of a resultant moment occurs which causes a turning effect
the lower the centre of mass and the bigger the base area, the more stable the object is
what does acceleration mean
the rate of change of an objects velocity
whats velocity
the rate of change of an objects displacement
whats displacement
how far an object has travelled from its starting point in a given direction
what’s an ultrasound position detector and what are advantages of it
it’s a tote of data logger that automatically records the distance of an object from the sensor several times a second
this helps get real time displacement-time and velocity-time graphs
adv.
- data is more accurate (faster reaction times)
- have higher sampling rate than humans (take ten readings very second)
- you can see the data displayed in real time
what are the 4 SUVAT equations
- a=(v-u)/t
- S=ut+1/2at^2
- v^2=u^2+2as
- S=(u+v)/2xt
what’s the free falls experiment
- measure the night from the bottom of the ball bearing to the trapdoor
- flick the switch to simultaneously start the timer and disconnect the electromagnetic, releasing the ball bearing
- the ball bearing falls, knocking the trapdoor down and breaking the circuit which stops the timer. record t
- repeat this experiment three times and average the time taken to fall from this height. repeat this experiment but drop the ball from several different heights
- you can then use these results to find the g using a graph
what can help getting a smaller uncertainly when doing the free fall experiment
by using a computer automatically release and time the ball bearings fall
how to calc the gradient of the free fall experiment
g= 2xs/t^2
what is a systematic and random error of the free fall experiment
random — effected by wind to remove this error conduct the experiment indoors and close all windows
systematic — there might be a delay in the stopwatch/light gates to remove this ensure they are properly calibrated before conducting the experiment
whats newton’s first law of motion
velocity of an object will not change unless a resultant force acts on it
whats newtons 2nd law
the more force you have acting on a certain mass the more acceleration you get
F=ma
in what direction does the acceleration go
the same direction as the resultant force
why did galileo say
he said that all objects fail at the same rate
whats newton’s second law
if an object A exerts a force on object B then object B exerts an equal but opposite force on object A
two ppl are diving and they reach the water at the same time why? explain in newtons 2nd laws
the force acting on each diver is their weight =mg since F=ma this gives the equation
mg=ma which can be written as g=a so their acceleration doesn’t depend on their mass but rather there gravitational sooo they reach the same time
what are the two types of friction
dry friction (solid friction)
fluid friction (drag) ( fluid resistance or air resistance )
