A.
Cite examples of "holistic" and "reductionist" thinking in a field
outside the natural sciences.
Holistic Medicine - treat the whole person
Reductionistic - treat specific organ or symptom
B.
A baseball is hit a long distance, slowed by air resistance, and
then caught. Detail the energy conversions that take place from the moment
it leaves hits the bat.
The ball initially has kinetic energy. This is converted to spring energy in the bat and
ball as they compress into each other and come to rest relative to each other. As they spring
apart, some of that energy is lost to heat, but the work done by the player on the bat (Force
times distance = push on bat handle in the direction the bat moves) adds
energy to the system. Now the ball has kinetic energy again. The air resistance does negative
work on the ball, reducing its kinetic energy (and speed). Also, as the ball rises, it's
gravitational potential energy increases, which reduces the kinetic energy by the same amount.
As the ball falls downward, its gravitational potential energy decreases, and this
increases the kinetic energy by the same amount. Finally the outfielder catches the ball,
doing enough negative work to stop the ball.
C.
Explain why more work must be done to acceleerate
a car from 60mph to 70mph than to accelerate it
from 0mph to 10mph.
Work = force time distance. In the 60 to 70mph case, the car moves through
a much larger distance than in the 0 to 10mph case. Second, the force in the
high speed case is more because the air resistance is so much larger.
5.
A cyclist climbs a hill 10 meters high on a road 100 meters long,
at a constant speed of 5m/s. The combined mass of bike and rider
is 70kg, and the force exerted to propel the bike is 100N.
a. How much work is done by the force?
W=f*d = 100N * 100m = 10,000 J
b. What is the increase in gravitational potential energy?
mgh = 70kg * 9.8m/s/s *10m = 6860J
e. How long does it take the cyclist to ride this distance? (C1 type problem)
time=dist/rate=100m/(5m/s)=20s
f. What is the cyclist's kinetic energy at the beginning? at the end?
K=0.5*m*vs = 0.5*70kg *(5m/s)^2 = 875 J. Same at end.
g. What is the cyclist's total energy at the beginning? at the end?
K+U =
c. What happens to the rest of the energy?
lost to friction and air resistance - heats air and bearings and tires
d. How much power (in watts) must the cyclist generate?
Convert this to horsepower.
P = W/t = 10000J/20s = 500 W = .67hp