The Mixed Journey
Distance vs the shortcut home
What this lesson covers
Why it matters
Walk all the way around the park and back to the gate. Your legs did 400 metres of work. Your position changed by… nothing at all. Both numbers are true.
Predict first
After one full lap of the park, your distance walked and your change of position are…
Distance counts every step of the path. The straight-line change of position (displacement) from gate to gate is zero.
- 400 m walked, but position changed by zero — correct
- both 400 m
- both zero
What you do
Walk the park grid: rack up 400 m of walking, then bring the shortcut arrow back to zero by coming home.
Check yourself
A ball thrown straight up and caught back has covered…
Up 5 m + down 5 m = 10 m of distance; start = end, so zero displacement.
A cyclist rounding a curve at steady 10 km/h is still CHANGING her…
Curved path = turning direction every moment, even at constant speed — a 'mixed' motion.
Your mass is 40 kg. The Earth''s PULL on you is called your…
Mass = how much stuff (40 kg anywhere). Weight = gravity''s pull on that stuff — on the Moon you''d weigh less but still be 40 kg of you.
- real distance, but zero net change of position — correct
- no distance
- double displacement
- direction of motion — correct
- speed
- nothing
- weight — it depends on gravity; mass is just your matter — correct
- mass — pull and mass are the same
- speed