Download Example 13.1 Billiards, Anyone? Three 0.300

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Categorize This example is a substitution problem.
Use Equation 13.22
to find the escape
speed:
Evaluate the kinetic
energy of the
esc
2  6.674 1011 N  m 2 kg 2  5.97 1024 kg 
2GM E


RE
6.37 106 m
 1.12 104 m s
2
K  12 mesc

1
2
 5.00 10
3
kg 1.12 104 m s 
2
 3.13 1011 J
spacecraft from
Equation 7.16:
The calculated escape speed corresponds to about 25 000 mi/h. The kinetic energy of
the spacecraft is equivalent to the energy released by the combustion of about 2 300
gal of gasoline.
WHAT IF? What if you want to launch a 1 000-kg spacecraft at the escape speed?
How much energy would that require?
Answer In Equation 13.22, the mass of the object moving with the escape speed does
not appear. Therefore, the escape speed for the 1 000-kg spacecraft is the same as that
for the 5 000-kg spacecraft. The only change in the kinetic energy is due to the mass,
so the 1 000-kg spacecraft requires one-fifth of the energy of the 5 000-kg spacecraft:
K  15  3.13 1011 J   6.25 1010 J
Objective Questions 1. denotes answer available in Student Solutions Manual/Study
Guide
1. A system consists of five particles. How many terms appear in the expression for
the total gravitational potential energy of the system? (a) 4 (b) 5 (c) 10 (d) 20 (e)
25
2. Rank the following quantities of energy from largest to smallest. State if any are
equal. (a) the absolute value of the average potential energy of the Sun–Earth