Friday maths problem.

[j2 lot]

I'm just waiting of the Youtube video of the car hitting the tree

[Corranga]

We need to know the colour, top speed and original cost of the car. That's what the press always seem to report...

[pete]

So, I felt so embarrassed I had to prove to myself I could still do higher physics.

The only things we know are initial velocity (v) and final velocity (u) of each car.
We don't know acceleration, time or distance.
But we can assume that acceleration (a) (deceleration in this case) is the same in both cars and we know that the distance (s) to the tree is the same for both cars, even though we don't know the actual numbers.

Use formula v^2 = u^2 +2as
Rearrange;
2as = v^2 - u^2

As we know that the deceleration and distance is the same for both cars we can say that;

(v^2 - u^2) for car 1 is equal to (v^2 - u^2) for car 2
or
v(car1)^2 - u(car1)^2 = v(car2)^2 - u(car2)^2

The one we are trying to work out is u(car1) (final speed of car one) so we can rearrange;

u1^2 = (v1^2)-(v2^2)+(u2^2)

Convert 70mph into 31.3m/s and 100mph into 44.7m/s

u1^2 = 1998 - 979 + 0
u1^2 = 1018
u1 = 31.9m/s

So final speed of car 1 as it hits the tree is 31.9m/s which is 71.4mph.

Anyone still awake?

Yes. You have more patience for typing than me. (Although you don't have to convert it to m/s, units are units).

And the first time I did it I got thirty and so did my wife (A level physics for me) which should make you feel better

[graeme]

This sounds like brake.org.uk propaganda to me. FAKE NEWS!

[Stevoraith]

You have more patience for typing than me.

I was at work. It was more interesting than actual work

[tut]

I have A Level Physics, well I got 5% so really only took the subject as opposed to passing it, so did not want to show you all up with doing it in my head.

tut