# Unit 1 mechanics (G481) motion

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• Created by: Elly
• Created on: 02-01-13 10:15
• Motion
• scalars
• a quantity with magnitude but not direction
• e.g. potential difference, speed, pressure, distance
• Free fall
• g=9.81ms^-2
• Trap door method
• electromagnet just supports a steel ball
• when current through the electromagnetis switched off theball starts to fall and the clock is triggered.
• balls falls onto trap door
• when trap  door breaks the clock is stopped.
• distance of fall is measured and so is the time taken.
• Repeats
• electromagnet just supports a steel ball
• when current through the electromagnetis switched off theball starts to fall and the clock is triggered.
• balls falls onto trap door
• when trap  door breaks the clock is stopped.
• distance of fall is measured and so is the time taken.
• Repeats
• theory
• s=ut+1/2at^2 . u is 0 as ball starts from rest.
• this gives s=1/2gt^2 and hence g=2s/t^2.
• a graph of s against against t^2 will have a gradient of g/2.
• Random uncertainty
• em current too large cause a delay in releasing ball. current must only just support ball.
• If distance is too large or ball to small air resistance may have a noticeable effect.
• ensure that distance is measured accurately from base of ball to trap door not the electromagnet to door.
• Vectors
• resolving
• horizontal and vertical components
• Calculations
• Trigonometry
• the length of the hypotenuse AC is 55.0mm and angle next to right angle is 72*.
• This makes the side adjacent to the angle         55.0xCos72*=17.0mm
• and the side opposite to the angle  =55.0xSin72*=52.3mm
• Pythagorus
• A llorry's load hass a weight of 40000NN and it is being pulledd along by a horizontal force of 15000N what is the resultant of these two forces?
• Resultant^2= (4.0x10^4)^2 + (1.5x10^4)^2 = 18.25x10^8 so resultant=4.27x10^4N
• a quantity with both magnitude and direction
• e.g. electric current, velocity, displacement, acceleration, force.
• constant acceleration  equations
• s u v a t
• s = displacement
• m
• u =  initial velocity v= end  velocity
• ms^-11
• a = acceleration
• ms^-2
• t = time
• s
• v=u+at
• s=1/2(u+v)t
• s=ut+1/2at^2
• v^2=u^2+2as
• graphs of motion
• Displacement-time  graphs
• velocity-time graphs