we gotta problem here guys=("tough Question"

User Name · #1 $Old$ May 22nd, 2008, 04:12 AM

Hi
I'm new and it's my first post

anyways can anyone help me to solve this Question it's really annoying

How fast?

Thanks

mr fantastic · #2 $Old$ May 22nd, 2008, 06:02 AM

Quote:

Originally Posted by User Name $View Post$

Hi
I'm new and it's my first post

anyways can anyone help me to solve this Question it's really annoying

How fast?

A spacecraft undergoes a journey of two separate legs. The second leg is twice as long as the first leg, and the average speed of the craft during the second leg is is 10% higher than its average speed during the earlier leg.
The spacecraft's average speed over the entire journey is 9660 km/h.
calculate its average speed for each leg.

Thanks

Let the average speed in first leg be v and let distance of first leg be x.

Then average speed in second leg is v + (v/10) = 11v/10 and distance of second leg is 2x.

Time to travel first leg: $t_1 = \frac{x}{v}$ .... (1)

Time to travel second leg: $t_2 = \frac{2x}{11v/10} = \frac{20 x}{11 v}$ .... (2)

Average speed for entire journey: $9660 = \frac{3x}{t_1 + t_2}$ .... (3)

Substitute (1) and (2) into (3) and solve for v (note that the x's cancel out).

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