Everything Science Grade 10

21.3 CHAPTER 21. MOTION IN ONE DIMENSION

The information is not in SI units and must therefore be converted.

To convert km to m, we know that:

1 km = 1 000m

∴ 2 km = 2 000m (multiply both sides by 2 .)

Similarly, to convert 30 minutes to seconds,

1 min = 60s

∴ 30 min = 1 800s (multiply both sides by 30)

Step 3:Determine James’ displacement and distance.

James started at home and returned home, so his displacement is 0 m.

∆~x= 0m

James walked a total distance of 4000 m (2 000m out and2 000m

back).

D= 4 000m

Step 4:Determine his total time.

James took1 800s to walk out and1 800s to walk back.

∆t= 3 600s

Step 5:Determine his average speed

vav = ∆Dt

= 4 0003 600ms

= 1, 11 m·s−^1

Step 6:Determine his average velocity

~vav = ∆∆~xt

= 3 600^0 ms

= 0 m·s−^1

398 Physics: Mechanics