Question

While running around the track at school, Milt notices that he runs due East on the 100m homestretch and due West on the 100m backstretch. To train for the 800m event, he runs both the 100m homestretch and the 100m backstretch in 12.2 seconds. How do Milt's velocities on the homestretch and backstretch compare? A) The homestretch and backstretch have velocities with the same magnitude only. B) The backstretch velocity is greater in magnitude than the homestretch velocity. C) The home stretch velocity is greater in magnitude than the backstretch velocity. D) The homestretch and the backstretch have velocities with the same direction and magnitude.

Answer 1

Answer a would be correct since velocity is a vector and has a magnitude and a direction. In this case v₁ = - v₂.

Answer 2

The correct answer is

A) The homestretch and backstretch have velocities with the same magnitude only.

Explanation:

Velocity is a vector - it means it consists of:

1) A magnitude: called speed, it is given by the ratio between the total distance covered, d, and the time taken, t:

$v=\frac{d}{t}$

2) A direction: the direction of motion

In this example, we see that the homestretch and the backstretch have same speed, because the same distance (100 m) is covered in the same time interval (100 m), however the direction is different (the homestretch is due East, while the backstretch is due West). So, the correct answer is

A) The homestretch and backstretch have velocities with the same magnitude only.