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Chapter 9: 9.Q. 2 (page 227)
At what speed does a 1000 kg compact car have the same kinetic energy as a 20,000 kg truck going 25 km/h?
The speed should be 11.8 km/hr.
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A kg sprinter, starting from rest, runs m in s at constant acceleration.
a. What is the magnitude of the horizontal force acting on the sprinter?
b. What is the sprinter鈥檚 power output at s, s, and s?
When you ride a bicycle at constant speed, nearly all the energy you expend goes into the work you do against the drag force of the air. Model a cyclist as having cross-section area and, because the human body is not aerodynamically shaped, a drag coefficient of .
a. What is the cyclist鈥檚 power output while riding at a steady ?
b. Metabolic power is the rate at which your body 鈥渂urns鈥� fuel to power your activities. For many activities, your body is roughly efficient at converting the chemical energy of food into mechanical energy. What is the cyclist鈥檚 metabolic power while cycling at ?
c. The food calorie is equivalent to How many calories does the cyclist burn if he rides over level ground at?
A kg particle moving along the axis experiences the force shown in FIGURE. The particle鈥檚 velocity is m/s at m. What is its velocity at m and m?
A kg human sprinter can accelerate from rest to m/s in s. During the same time interval, a kg greyhound can go from rest to m/s. What is the average power output of each? Average power over a time interval is
Evaluate the dot product if
a. and .
b. and.
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