Question

A person walks first at a constant speed of 5.10 m/s along a straight line from point circled a to point circled b and then back along the line from circled b to circled a at a constant speed of 2.75 m/s. (a) what is her average speed over the entire trip? 3.57 correct: your answer is correct. m/s

Answer 1

Average speed = total distance / time

1) Distance from A to B

Distance = velocity * time  = V1 * t1 = 5.10 t1

2) Distance from B to A

Distance = velocity * time  = V2*t 2 = 2.75 t2

Distance from A to B = distance from B to A => 5.10t1 = 2.75t2

=> t2 = 5.10t1 / 2.75

3) Average speed = total distance / total time =

total distance = 2 * 5.10 t1 = 10.20 t1

Average speed = [10.20 t1] / [t1 + 5.10 t1 / 2.75]

As you see t1 is factor for the three terms, so you can simplify it

=> Average speed = [10.20 ] / [1 + 5.10/2.75] = 3.57 m/s

Answer: 3.57 m/s