Summary

• Units
• Conversion factors
• Significant figures

• Reading Quiz
  
  
• Motion in one dimension

  displacement Δx average speed Example #1 velocity Example #2 instantaneous velocity applet Example #3 acceleration Example #4

  Jamaica's Usain Bolt cruises to the finish of the 100-meter final in Berlin, Germany, August 16, 2009. He set the world record after completing the race in 9.58 seconds.

  
  
  

wk4
Reading quiz The magnitude of the instantaneous velocity is called the _____.
A. acceleration
B. instantaneous speed
C. vector momentum
D. cumulative impulse
Answer











sj6 2.5a
A person walks from A to B at 5.00 m/s and returns to A at 3.00 m/s. What is her average speed?
A. 0 m/s
B. 3.00 m/s
C. 3.75 m/s
D. 4.00 m/s
Answer











sj6 2.5b
A person walks from A to B at 5.00 m/s and returns to A at 3.00 m/s. What is her average velocity?
A. 0 m/s
B. 3.00 m/s
C. 3.75 m/s
D. 4.00 m/s
Answer











kw4 2.q23
A trucker drives 320 km between noon and 4 P.M. What is the instantaneous speed of the truck at 2 P.M.?
A. 80 km/h
B. 160 km/h
C. 320 km/h
D. can't say

Answer



















kw4 1.q35
A racecar accelerates from 120 mph to 128 mph in 2 seconds. A runner accelerates from 0 to 10 mph in 2 seconds. Which has the larger acceleration?
A. racecar
B. runner
C. they're the same
Answer















 



B. instantaneous speed





















 



C. 3.75 m/s





















 



A. 0 m/s
The net displacement is zero!




















 



D. can't say
With distance and time information we can only calculate average speed, not instantaneous velocity.












 



B. runner
The runner has a smaller speed but a larger acceleration.