* BIO Internal energy change while biking You set your stationary bike on a high 80-N friction-like resistive force and cycle for 30 min at a speed of 8.0 m/s. Your body is 10 % efficient at converting chemical energy in your body into mechanical work. (a) What is your internal chemical energy change? (b) How long must you bike to convert 3 .0 × 10 5 J of chemical potential while staying at this speed? (This amount of energy equals the energy released by the body after eating three slices of bread.)
* BIO Internal energy change while biking You set your stationary bike on a high 80-N friction-like resistive force and cycle for 30 min at a speed of 8.0 m/s. Your body is 10 % efficient at converting chemical energy in your body into mechanical work. (a) What is your internal chemical energy change? (b) How long must you bike to convert 3 .0 × 10 5 J of chemical potential while staying at this speed? (This amount of energy equals the energy released by the body after eating three slices of bread.)
* BIO Internal energy change while biking You set your stationary bike on a high 80-N friction-like resistive force and cycle for 30 min at a speed of 8.0 m/s. Your body is
10
%
efficient at converting chemical energy in your body into mechanical work. (a) What is your internal chemical energy change? (b) How long must you bike to convert
3
.0
×
10
5
J
of chemical potential while staying at this speed? (This amount of energy equals the energy released by the body after eating three slices of bread.)
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 7 Solutions
Pearson eText for College Physics: Explore and Apply -- Instant Access (Pearson+)
Physics for Scientists and Engineers: A Strategic Approach, Vol. 1 (Chs 1-21) (4th Edition)
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