Question

Two boats start together and race across a 68-km-wide lake and back. Boat A goes across at 68 km/h and returns at 68 km/h. Boat B goes across at 34 km/h, and its crew, realizing how far behind it is getting, returns at 102 km/h. Turnaround times are negligible, and the boat that completes the round trip first wins.

a. Which boat wins and by how much?
b. What is the average velocity of the winning boat?

Answer 1

a

The winning boat is boat A

b

`v_(avg) =0 m/s`

Step-by-step explanation:

From the question we are told that

The width of the lake is
`w =  68 \  km`

The speed of boat A to and fro is
`v_a  =  68km/h`

The speed of boat B going is
`v_b  =  34 km/h`

The speed of boat B coming back is
`v_B =  102 \ km/h`

Generally the time taken by boat A is mathematically represented as

`t_A  =   (w)/( v_a)  + (w)/( v_a)`

`t_A  =  (68)/(68)  +  (68)/(68)`

`t_A  =  2 \  hours`

Generally the time taken by boat B is mathematically represented as

`t_B  =   (w)/( v_b)  + (w)/( v_B)`

`t_B  =   (68)/( 34)  + (68)/( 102)`

`t_B  =  2.67 \ hours`

The winning boat is boat A

The average velocity is mathematically represented as

`v_(avg) =  (v_a  -  v_a)/( d)`

Here d is the total displacement of the winning boat which is 0 m

So

`v_(avg) =  (68  -  68)/(0)`

`v_(avg) =0 m/s`