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VCE Stuff => VCE Science => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Physics => Topic started by: tolga on February 13, 2010, 12:24:07 pm

Title: Motion question help
Post by: tolga on February 13, 2010, 12:24:07 pm: A cyclist is taking part ofa race. The mass of the cyclist and bicycle is 75kg. The cyclist, starting from rest, applies a constant driving force and is travelling at a constant speed 16metres from the start. The graph below shows the total resistance forces appled to cyclist and bicycle over the first 20 metres of the race.

C:\Users\tolga\Pictures\Graph.jpg

a)What is the magnitude of the net force acting on the cyclist and bicycle at a distance of 19m from the start? Justify your answer.
b)What is the magnitude of the constant driving force provided by the cyclist?
c)What is the magnitude of the acceleration of the cyclist and bicycle at a distance of 6m from the start?
Title: Re: Motion question help
Post by: m@tty on February 13, 2010, 02:21:12 pm: a) $F_{net}=0$ as he is travelling at constant speed at this stage.

b) $F_{net}=Driving force + Resitance$ As driving force is constant, and $F_{net}=0$ at anypoint after 16m. At 16m Resistance=110 back. Therefore $0=Driving force -110$ so driving force is 110 N.

c) Assuming at 6m resistance is 20 N
$m=75 \ kg$

$F_{net}=Driving force + Resistance = 110 -20 = 90 N$

$\begin{align} F&=ma \\ 90&=75 \cdot a \\ \therefore a&=\frac{90}{75} = 1.2 \ ms^{-2} \end{align}$

Hopefully it is correct. :)
Title: Re: Motion question help
Post by: tolga on February 13, 2010, 02:49:43 pm: Thanks alot now i get it. :)
Title: Re: Motion question help
Post by: m@tty on February 13, 2010, 02:55:38 pm: No problem. :)