How far will a motorcycle travel before coming to a halt?

[Kartik.]

1. A uniformly retarded moving motorcycle covers 250 meters in the first 10 seconds and and 250 meters in the next 20 seconds.How much will it travel more to come before coming to a halt?


250 = 10u - 50a , 250 = 20u - 200a. On solving these i get and a retardation of 2.5.

 

[cepheid]

1. A uniformly retarded moving motorcycle covers 250 meters in the first 10 seconds and and 250 meters in the next 20 seconds.How much will it travel more to come before coming to a halt?


250 = 10u - 50a , 250 = 20u - 200a. On solving these i get and a retardation of 2.5.

Although it is hard to understand your work, which was not well explained, I get that you applied the equation d = ut + (1/2)at² twice, once for each time period. This is the correct thing to do.

Did you assume that 'u' was the same between both equations? Because it's not the same u. The u in your first equation is the initial velocity at the beginning of the 10 second period. The u in your second equation is the initial velocity at the beginning of the 20 second period. These are not the same, but you can *relate* them using the equation for speed vs time.

 

[T-chef]

An alternative method to the one above, that gives you two equations with the same u (initial velocity) would be to use the fact that you know how far the bike has traveled after 30 seconds :)