Still, and Still Accelerating
Leo throws a ball straight up at 14.7 m/s. It rises for 1.5 s, stops for an instant about 11 m up, and falls back into his hand 1.5 s later.
What is the ball’s acceleration at the instant it stops at the top?
Page 1
Science · Physics
Chapter 1: Measurement and Motion in One Dimension
A change in velocity, in any respect.
Leo throws a ball straight up at 14.7 m/s. It rises for 1.5 s, stops for an instant about 11 m up, and falls back into his hand 1.5 s later.
What is the ball’s acceleration at the instant it stops at the top?
Make your guess to turn the page.
Still to come: 10 pages · Lab · Words to Know · What We Learned · 4 questions · Explain It in Writing · Open Questions
The idea this lesson is working on — Students read a negative acceleration as slowing and zero velocity as zero acceleration. The sensor data sets both against one straight velocity graph that passes through zero without changing slope. Ask: is the velocity changing at the top, and do v and a share a sign? The idea to reach is that acceleration is the rate of change of velocity, and speeding up means the signs agree.
A change in velocity, in any respect — Speeding up, slowing down and turning are all accelerations, because velocity includes direction; this chapter stays on a line. Stapp's run (Sonic Wind No. 1, December 1954) reached about 632 mph; the peak deceleration recorded was about 46 g, and the 1.4 s stop is approximate.