Which Cart Is Faster?
Leo's cart and Ben's cart zoom down the hall, one after the other. Everyone watching says they look just as fast.
Were the two carts really going at the same speed?
Page 1
Science · Grade 4 Science
Chapter 1: Energy and Motion
A number you can check beats a word.
Leo's cart and Ben's cart zoom down the hall, one after the other. Everyone watching says they look just as fast.
Were the two carts really going at the same speed?
Make your guess to turn the page.
Still to come: 9 pages · Words to Know · What We Learned · 4 questions · Explain It in Writing · Ask and Wonder
The idea this lesson is working on — Children trust their eyes about speed. The two hall runs are drawn to look the same, and everyone in the story calls it a tie; the stopwatch says 3 m/s against 4 m/s, and the block says 9 units of energy against 16. Ask: how would you convince someone who was not there? "Fast" means different things to different people; distance divided by time gives a number anybody can check.
A graph shows the pattern — Plotting distance against time makes a steady speed a straight line and a changing speed a curve, and the steeper line is the faster one. The book draws both carts at a steady speed to keep one idea at a time; a real cart slows a little as it rolls, so its line would bend slightly.