Chapter 2 Physical Science

Question

Ch 2 Discussion

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Answer the questions below, after reading Chapter 2 "Motion". Make sure that you give your answer in a clear and justified manner, providing necessary explanation on how you came up with it.  Show all initial formulas, calculation steps, units, and the final answer (with units as well). Note, that simply posting the answer without a detailed explanation/solution won't count for credit. Post your initial thread first by Thu, and then reply to the posts of at least 3 peers by Sun. In order to reply, click on the peer's thread first, then click reply. In your peer reply, provide a detailed and constructive feedback to your classmate. The reply looking like “awesome job!” doesn’t count.  

 

Question 1:  a). A student jogs around a circular track with a diameter of 1.0 km in 30 minutes. Find the runner’s average speed in meters per second (m/s). 

                      b). Now convert this speed into kilometers per hr, and miles per hour, in order to practice the unit conversion. 

Question 2:  A sprinter starting from rest on a straight lever track is able to achieve a speed of 25 m/s in 14 s. What is the sprinter’s average acceleration (please accompany your answer with the proper acceleration units, m/s²)?

Answer 1

1:  a). A student jogs around a circular track with a diameter of 1.0 km in 30 minutes. Find the runner’s average speed in meters per second (m/s). 

Given:

d = 1km = 1000m ==> Circumference = πd = 3.14 x 1000 = 3140m

t = 30 min = 1800s

V_av = d/t = 3140m/1800s = 1.744 m/s ~ 1.7 m/s

                     

b). km/h ==> 3.14/0.5h = 6.28 km/h

3.14 km = ?miles ==> 1 km = 0.621371 miles so 3.14 x 0.621371 = 1.9511 miles/h =~ 2 mph

2) acceleration = change in velocity/time

a = ΔV/Δt

a = +25 m/s / 14s = 1.78571428571 m/s² Rounded down to 1.8 m/s²

I hope this helps. Thanks