Some Physics questions. [Kinematics O.O]

davidche SG · 2008-10-17T09:44:45+00:00

the formulae is not in the syllabus anymore. So you need to use another way to do it.anyway, 1A) velocity = acceleration x time= 2 x 10= 20m/s1B), KE = half...

skythewood SG

Sry im missing some link XD. With what formula do you subsitute your t with?

If it is using s = ut + ½at², how do you get this formula?

Thanks

assume acceleration is constant.

let's say from A to B. s is the area under the graph.

s = (A +B)/2 x t

= At/2 + Bt/2

=At/2 + (A + at)t/2 (v = u + at)

= At/2 + At/2 + (at^2)/2

=At + (at^2)/2

eagle SG

Sry im missing some link XD. With what formula do you subsitute your t with?

If it is using s = ut + ½at², how do you get this formula?

Thanks

for s = ut + ½at²

Draw your velocity time graph, starting from u at t=0 and ending at v at t =t (all draw positive for simplicity)

Area under graph is a rectangle plus a triangle.
Area of rectangle will give ut
Are of triangle will give ½(at)(t), where at is v - u

Sum up, you will get the formula ;)

Finally, from a = (v-u)/t,
t = (v-u)/a
Sub into s = ut + ½at²

Resolve and simplify, you will get v² = u² + 2as

davidche SG

I understand liao. Thanks guys

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