A bicycle racer sprints at the end of a race to clinch a victory. The racer has

Physics
Tutor: None Selected Time limit: 1 Day

A bicycle racer sprints at the end of a race to clinch a victory. The racer has an initial velocity of 12.5 m/s and accelerates at the rate of 0.550 m/s2 for 7.00 s.
(a) What is his final velocity?
 m/s
(b) The racer continues at this velocity to the finish line. If he was 300 m from the finish line when he started to accelerate, how much time did he save?
 s
(c) One other racer was 5.00 m ahead when the winner started to accelerate, but he was unable to accelerate and traveled at 12.7 m/s until the finish line. How far ahead of him (in meters and in seconds) did the winner finish?
distance
 m
time
 s
Sep 8th, 2015

Thank you for the opportunity to help you with your question!

a) V1 = Vo + a*t
=12.5 + 0.550*7
= 16.35 m/s
distance  = 12.5*7 + 0.275*7^2 = 100.975 m.
b)
d = V1*T2 = 300-100.975 = 199.025
16.35*T2 = 199.025
T2 =  12.17278 s
T1+T2 = 7 + 12.17278 =  19.17278 s. To travel 300 m with acceleration.

d = Vo*T3 = 300 m.
12.5*T3 = 300.
T3 = 24 s. To travel 300 m without accelerating.

T = T3-(T1+T2) = 24 - 19.17278 = 4.82722 s Saved.

I will post the last part soon



Please let me know if you need any clarification. I'm always happy to answer your questions.
Sep 8th, 2015

Part c

d = V*T = 300-5 = 295 m.
12.7 * T = 295.
T = 23.22835 s. To finish.

23.22835 - 19.17278=  4.05557 s. Behind the winner.

300m/19.17278s * 4.05557s. = 63.46 m. Behind the
winner.

Sep 8th, 2015

Sry,but the a was wrong

Sep 8th, 2015

and the c was wrong too

Sep 8th, 2015

Let me see, How I made it wrong. I guess its because such kind of questions come with a short time of 20 minutes thus the pressure can cause one to do a mistake.

Sep 8th, 2015

Maybe

Sep 8th, 2015

I really cant get it with the first one

the formula is

v= u + at where v is  the final velocity, u is the initial velocity  and a the acceleration while t is the time

so it becomes

v= 12.5 + 0.550  x 7

v= 12.5 +3.85

v=16.35 m/s

Sep 8th, 2015

(A) is right but the (c) is wrong too_____m

Sep 8th, 2015

You know I was shocked to hear that A was wrong. I even felt like giving up on doing them. Let me go through C and see what value I have done wrongly.. Thanks

Sep 8th, 2015

Thanks

Sep 8th, 2015

d = V*T = 300-5 = 295 m.
12.7 * T = 295.
T = 23.22835 s. To finish.

23.22835 - 19.17278=  4.05557 s. Ahead

In Meters
time traveled at finish of winner
=19.17278s
D = s x time
=12.5 x  19.17278
= 239.6598 m
subtract it from the total distance of 295
=295- 239.6598
= 55.3402

I had plugged in the figure for the winner instead of for the guy in position 2
300m/19.17278s * 4.05557s. = 63.46 m. Behind the
winner.



Sep 8th, 2015

Sry but it`s still wrong

Sep 8th, 2015

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