Calculating Velocity/Speed of a Lost Coin

[cbrowne]

Hello could someone please check this question for me. Thanks

Homework Statement

On her way to school, a child discovered that her loonie is missing and there is a
hole in her pocket. In searching for the missing coin, the child turned back and
walked for 9.5 m, along the sidewalk. Then she turned forward and walked for
3.2 m and then turned back again and walked for 17.8 m before finding her
loonie.
(a) What is the total displacement of the child?
(b) If the child spent 8.5 minutes searching for the coin, what was her average velocity? (c) What was her average speed?

Homework Equations

The Attempt at a Solution

a) Δ x = -24.1 m

b) V average = Δx/ Δt = -24.1m/ 8.5 min x 60 secs = 0.047255 m /s

c) S avg = d1+d2+d3/ Δt

S avg = 9.5m+ 3.2m + 17.8 m/8.5min x 60 secs = 0.059804 m/s

 

[Redbelly98]

Your answers look good mathematically. I do have 2 comments:

1. For the time conversions, you should use 60 sec/min, not 60 sec. Doesn't change the number, but it makes a difference in the units you get and how you think about the units.

2. We know the distances and times to just 2 or 3 significant figures. So your final answers are given to a lot more accuracy than is justified.