Careful measurements have been made of Olympic sprinters in the 100 meter dash. A simple but reasonably accurate model is that a sprinter accelerates at 3.6 m/s 2 for 3 1 3 s, then runs at constant velocity to the finish line. a. What is the race time for a sprinter who follows this model? b. A sprinter could run a faster race by accelerating faster at the beginning, thus reaching top speed sooner. If a sprinter’s top speed is the same as in part a, what acceleration would he need to run the 100 meter dash in 9.9 s? c. By what percent did the sprinter need to increase his acceleration in order to decrease his time by 1%?
Careful measurements have been made of Olympic sprinters in the 100 meter dash. A simple but reasonably accurate model is that a sprinter accelerates at 3.6 m/s 2 for 3 1 3 s, then runs at constant velocity to the finish line. a. What is the race time for a sprinter who follows this model? b. A sprinter could run a faster race by accelerating faster at the beginning, thus reaching top speed sooner. If a sprinter’s top speed is the same as in part a, what acceleration would he need to run the 100 meter dash in 9.9 s? c. By what percent did the sprinter need to increase his acceleration in order to decrease his time by 1%?
Careful measurements have been made of Olympic sprinters in the 100 meter dash. A simple but reasonably accurate model is that a sprinter accelerates at 3.6 m/s2 for
3
1
3
s, then runs at constant velocity to the finish line.
a. What is the race time for a sprinter who follows this model?
b. A sprinter could run a faster race by accelerating faster at the beginning, thus reaching top speed sooner. If a sprinter’s top speed is the same as in part a, what acceleration would he need to run the 100 meter dash in 9.9 s?
c. By what percent did the sprinter need to increase his acceleration in order to decrease his time by 1%?
You are working with a team that is designing a new roller coaster-type amusement park ride for a major theme park. You are present for the testing of the ride, in which an empty 150 kg car is sent along the entire ride. Near the end of the ride, the car is at near rest at the top of a 100 m
tall track. It then enters a final section, rolling down an undulating hill to ground level. The total length of track for this final section from the top to the ground is 250 m. For the first 230 m, a constant friction force of 370 N acts from computer-controlled brakes. For the last 20 m, which is
horizontal at ground level, the computer increases the friction force to a value required for the speed to be reduced to zero just as the car arrives at the point on the track at which the passengers exit.
(a) Determine the required constant friction force (in N) for the last 20 m for the empty test car.
Write AK + AU + AE int
= W+Q + TMW
+
TMT + TET + TER for the car-track-Earth system and solve for…
=
12 kg, and m3
Three objects with masses m₁ = 3.8 kg, m₂
find the speed of m3 after it moves down 4.0 m.
m/s
19 kg, respectively, are attached by strings over frictionless pulleys as indicated in the figure below. The horizontal surface exerts a force of friction of 30 N on m2. If the system is released from rest, use energy concepts to
m
m2
m3
i
Three objects with masses m₁ = 3.8 kg, m₂ = 12 kg, and m 19 kg, respectively, are attached by strings over frictionless pulleys as indicated in the figure below. The horizontal surface exerts a force of friction of 30 N on m2. If the system is released from rest, use energy concepts to
find the speed of m¸ after it moves down 4.0 m.
m/s
m
m2
mg
Chapter 2 Solutions
Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)
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