knowledge, science, and the universe chapter 1 - Physical Science ...

Study Guide 39
7. The Sun has much more mass than Earth (about
330,000 times as much). Why aren’t we pulled
toward the Sun with 330,000 times as much force
as we are toward Earth
8. Compare the weight and mass of a baseball in four
locations:
a. On Earth’s surface
b. In orbit around Earth at an altitude of about 100
miles.
c. On the Moon’s surface
d. Outside the solar system far from any planet.
9. Compare the definitions of weight and mass. Why
does the weight of an object change from place
to place while the mass does not
10. A cannonball, originally at rest, and a marble, originally
at rest, are dropped in a vacuum from the
same height at the same time.
a. What happens when they are dropped
Compare the speed and acceleration of the
cannonball with that of the marble.
b. Is the gravitational force of attraction larger on
the cannonball than it is on the marble Justify
your answer using a fundamental law.
c. Does the cannonball require a larger force to provide
the same acceleration as the marble Justify
your answer using the Second Law of Motion.
d. Explain how the cannonball with greater mass and
a greater force of gravity still has the same motion
as a marble with a lower mass and lower force of
gravity being dropped from the same height.
11. How many forces are acting on the Moon What
force keeps the moon moving around Earth
Synthesis
1. A penny and a feather fall toward Earth in a vacuum
tube. They begin falling at the same time.
a. Describe what would be observed.
b. Which of Newton’s laws apply to this scenario
c. Use the laws of motion that you listed in (b) to
explain what would occur.
2. A ride at an amusement park straps you into a seat
and raises you 400 feet above the ground. Once
you reach the top, you are dropped. Near the bottom,
a spring slows your descent.
a. What forces act on you during the ride When is
each force acting on you
b. What laws of motion would be relevant as you
travel from the top to the bottom of the ride
c. What is the rate of your acceleration when you
are in the middle of falling What law tells you
the rate of acceleration
d. In the middle of falling, you feel weightless.
Explain why.
e. What is the direction of the net force at the
bottom
3. Two identical encyclopedias are dropped. Encyclo -
pedia A is dropped from five feet off the ground
and Encyclopedia B is dropped from ten feet off
the ground. Encyclopedia B is dropped first. When
Encyclopedia B reaches exactly five feet above
the ground, Encyclopedia A is dropped.
a. Which encyclopedia has the greater force and
thus the greater acceleration acting on it
b. Which encyclopedia hits the ground first
c. Which encyclopedia is travelling faster when it
hits
d. Both Encyclopedia A’s and B’s covers hit the
ground face down. Does Encyclopedia A or
Encyclopedia B exert the greater force on the
ground
4. You take your 20-lb bowling ball on a trip with you
to the distant planet Sophia. The planet Sophia has
double the mass and half the diameter of Earth.
Answer the following questions about the bowling
ball.
a. What is the ball’s mass on Sophia
b. Relative to Earth, what is the bowling ball’s weight
c. Using the Law of Universal Gravitation, explain
how your answers in (a) and (b) are consistent
with one another.
d. If dropped on the planet Sophia, how does the
bowling ball’s acceleration compare to its acceleration
on Earth
e. You and your bowling buddies decide to race
your bowling balls by dropping them from the
same height somewhere on Sophia. Your friend’s
ball weighs 25 lbs on Earth, a mere fraction of
what your ball weighs on Sophia. Which ball hits
first
f. Which principle of symmetry from Chapter 1
applies to this question
5. Newton’s second law says F = ma. But the law of
gravity says F = GMm/d 2 . Explain why you need
both laws. Which aspect of a falling rock’s motion
is described by F = ma and which aspect is
described by F = GMm/d 2