How much would a 760 kg car
weigh on Venus?
•Mass of Venus: 4.89 x 1024 kg
•Radius of Venus: 6.05 x 106 m
•G = 6.67 x 10-11 N m2/kg2
For an object being swung from
the end of a string in a vertical
circle, where in the circular path
is the string most likely to
break?
The string is most likely to break when the
object is at the bottom of the circular path.
A distance of 6.00 mm separates
two particles of equal mass. If the
gravitational force between them is
6.80 x 10-4 N, what is the mass of
each particle?
• G = 6.67 x 10-11 N m2/kg2
How does the gravitational force
of attraction change between 2
objects if the mass of A triples
and the mass of B
quadruples?
• The force between the two objects will increase
by a factor of 12.
You can swing a bucket of water
around in a vertical circle and the
water will not come out of the
bucket. What keeps the water in
the bucket? Explain.
• The water’s inertia keeps it in the bucket. The
water resists changes in its motion, so it “wants”
to keep moving in a straight line path. Since the
bucket follows a curved path, it catches the
water before it can fall out of the bucket.
If the bottom of the bucket fell out
when the bucket was located
halfway along the upward side of
the circular path, describe the
resulting motion of the water.
• The water would move in a straight line path in
the upward direction. With the bottom of the
bucket gone, there is no longer a normal force
pushing the water into a circular path.
A child twirls a yo-yo about in a
horizontal circle. The yo-yo has a
mass of 0.30 kg and is attached to
a string 0.90 m long. If the speed
of the yo-yo is 1.5 revolution per
second, a) what tension must exist
in the string? b) What is the
centripetal acceleration of the yoyo?
Two cars travel around the
same curve, car A at twice the
speed of car B. Which car
experiences the larger
acceleration? How much
larger?
Car A has 4 times the acceleration as B.
Two cars travel around the
same curved, flat road with the
same constant speed. If car A
has twice the mass as car B,
which car experiences the
greater centripetal force? How
much larger?
Car A has twice the Fc as car B.
A 2.5-kg mass is attached to a
string 1.5 meter long and swings in
a circle parallel to the horizontal.
The mass goes around its path
once each 0.70 s. Calculate a) the
centripetal acceleration of the
object, and b) the tension in the
string.
A car travels at the same
constant speed around two
curves, curve A having 3 times
the radius of curve B. For which
of these curves is the car's
acceleration larger? How much
larger?
How would the gravitational
force between two objects be
affected if the distance
between them were reduced
by a third?
• The force between the objects would increase
by a factor of 9.
What is the direction of the net
force on a car that travels
around a flat, circular track with
a constant speed? What
actually supplies this net force?
Toward the center; friction.
If Brian (mass = 78.0 kg) weighs
himself and finds that he weighs
80.0 pounds, how far away from
the surface of the earth is he?
•
•
•
•
Earth’s mass  5.98 x 1024 kg
Earth’s radius  6.38 x 106 m
G = 6.67 x 10-11 N m2/kg2
1 lb. = 4.545 N
An astronaut on Mars weighs
200.9 N at the top of Olympus Mons,
the tallest mountain in our solar
system. If this astronaut weighs
204.1 N at the surface of Mars, what
is the height of Olympus Mons?
• Mars’ mass  6.43 x 1023 kg
• Mars’ radius  3.40 x 106 m
• G = 6.67 x 10-11 N m2/kg2
A 45.0 kg girl rides a Ferris
Wheel that has a diameter of
21.0 m. If the force of the seat
on the girl is 388 N at the top of
the ride, how fast is the ride
going?
What is the maximum safe
speed for the Ferris Wheel in
the previous problem
(diameter = 21.0 m)?
Seth and Gina ride a roller
coaster that has an inverted
loop. When they are at the top
of the loop, Gina observes that
she feels precisely 1/5 as heavy
as she normally does. If the
radius of the loop is 7.41 m,
how fast are they moving?
What is the minimum safe
speed for the roller coaster in
the previous situation?
(radius = 7.41 m)
How heavy will 68.0 kg Seth
feel when they reach the bottom
of the vertical loop, if the roller
coaster is moving at 15.5 m/s at
that point? How many g’s is
this?
On a scale from 1-10, how ready do
you feel for this test?
Why isn’t it a 10?