Summary

• Describing motion
• Average & instantaneous speed
• Acceleration

• Kinematic equations (Table 2-1 p.24)
  


Example #1
Example #2
Example #3


• Free fall

• a = −g = −9.80 m/s²
Example #4


• bowling ball & feather demo video
• On the moon video
Example #5

 

NASA transcript of Moon experiment


• Using ratios
Example #6

pop5 2.19
A truck covers 40 m in 8.5 s while smoothly slowing down to a final speed of 2.80 m/s. What was its initial speed?
A. 2.90 m/s
B. 3.50 m/s
C. 5.25 m/s
D. 6.61 m/s
Answer



















HRW10e 2.36
A car moves along a straight line through a distance of 900 m, starting and ending at rest. Through the first 225 m its acceleration is +2.25 m/s² and through the final 675 m its acceleration is −0.750 m/s². What is its travel time?
A. 56.6 s
B. 600 s
C. 1012.5 s
D. 2000 s
Answer



















pop5 2.20
A jet lands at 100 m/s and can brake at −5.00 m/s² maximum. What minimum runway length does it require?
A. 800 m
B. 1000 m
C. 2000 m
D. 5000 m
Answer



















klm
A cartoon gopher falls for 6.50 s before landing at the bottom of his hole. How deep is the hole?
A. 207 m
B. 31.9 m
C. 9.80 m
D. 6.50 m
Answer



















pop5 2.35
At t = 0 a ball is thrown directly downward with v₀ = −8.00 m/s from a height of 30.0 m. When does it land?
A. 3.75 s
B. 3.00 s
C. 1.79 s
D. 0.85 s
Answer




















sb5 2.34
A bullet strikes a 10-cm-thick board at 420 m/s and emerges at 280 m/s. How thick should the board have been to stop the bullet?
A. 28.0 cm
B. 23.3 cm
C. 18.0 cm
D. 15.0 cm
Answer







































answer

D. 6.61 m/s
The question neither mentions nor asks for the acceleration, so we choose the "no acceleration" equation:




















 

A. 56.6 s
The question neither mentions nor asks for the velocity at x = 225 m, which is the final velocity for the first interval and the initial velocity for the second interval. Hence we choose the "final velocity free" equation for the first interval and the "initial velocity free" equation for the second interval:




















answer

B. 1000 m
The question neither mentions nor asks for the time, so we choose the "time free" equation:




















answer

A. 207 m

answer

C. 1.79 s




















answer

C. 18.0 cm