Question

Selena and Brianna are running around a 400.0 meter long circular track. Selena runs all the way around the track In 58.8 seconds and Brianna runs halfway around the track in 52.0 seconds. Who had the fastest velocity. Explain

Answer 1

Brianna

Step-by-step explanation:

The question is asking for velocity, not speed. Velocity is displacement/time.

Since Selena runs all the way around the track, her displacement is zero, meaning she started and finished at the same point. Therefore, Selena's velocity = 0.

Brianna goes halfway around. Her displacement is the straight-line distance from the start point to the half-way point around the track. Circumference of a 400 m circular track = C = 400 m = 2πr. Solve for r:

r = 400/2π = 63.7 m

D = 2r = 127.3 m this is Brianna's displacement

Brianna's velocity = 127.3 m/52 s = 2.45 m/s

Therefore, Brianna has the fastest velocity.

Note: you really don't have to calculate Brianna's velocity to know that her velocity is > 0