Download 5th set - Nathan Dawson

Circular motion
For uniform circular motion the ACCELERATION is
directed toward the center of the circle at all times.
The magnitude of the radial
acceleration is given by
Dynamics of circular motion
For uniform circular motion the NET FORCE is
directed toward the center of the circle at all times.
The net force in the radial
direction is given by
When a ball on the end of a string swings in a vertical circle
with uniform circular motion, the ball is accelerating because
A.
B.
C.
D.
the speed is changing.
the direction is changing.
the speed and the direction are changing.
the ball is not accelerating.
When a ball on the end of a string is swung in a vertical circle
with uniform motion:
What is the direction of the acceleration of the ball?
A.
B.
Tangent to the circle, in the direction of the ball’s
motion
Toward the center of the circle
For the ball on the end of a string moving in a vertical circle:
What force is producing the centripetal acceleration of the ball?
A.
B.
C.
D.
gravity
air resistance
normal force
tension in the string
For the ball on the end of a string moving in a vertical circle:
What is the direction of the net force on the ball?
A. tangent to the circle
B. toward the center of the circle
C. there is no net force
A 0.150 kg ball on the end of a 1.10 m long, lightweight cord is
swung in a vertical circle. Determine the minimum speed the
ball must have at the top of its arc so that the ball continues
moving in a circle.
Circular motion and vehicles
The road exerts an inward force (friction against the tires) on
a car to make it move in a circle. The car exerts an inward
force on the passenger.
When a car turns a corner on a level road, which force provides the
necessary centripetal acceleration?
A.
B.
C.
D.
E.
Friction
Tension
Normal force
Air resistance
Gravity
A coin sits on a rotating
turntable.
1. At the time shown in the
figure, which arrow gives the
direction of the coin’s
velocity?
Additional Questions
A coin sits on a rotating
turntable.
2. At the time shown in the
figure, which arrow gives the
direction of the frictional
force on the coin?
Additional Questions
A coin sits on a rotating
turntable.
3. At the instant shown,
suppose the frictional force
disappeared. In what
direction would the coin
move?
When the ball reaches the break in the circle, which path will it follow?
A 1000 kg car rounds a curve on a flat
road of radius 50 m at a speed of 15 m/s.
(a) Will the car skid when the pavement
is dry and the coefficient of static
friction is 0.60?
(b) Will the car skid when the pavement
is slick and the coefficient of static
friction is 0.25?
A ball is rolled along the
inside of a partial
cardboard hoop lying flat
on a table. Which path
will the ball follow when
it gets to the end of the
hoop?
A car is rolling over the top of a
hill at speed v. At this instant,
A. n > w.
B. n < w.
C. n = w.
D.We can’t tell about n without knowing v.
A car of mass 1500 kg goes over
a hill at a speed of 20 m/s. The
shape of the hill is approximately
circular, with a radius of 60 m, as
in the figure at right. When the car
is at the highest point of the hill,
a. What is the force of gravity
on the car?
b. What is the normal force of
the road on the car at this
point?
A rider in a “gravitron” finds
herself stuck with her back to
the wall. Which diagram
correctly shows the forces
acting on her?
Newton’s Law of Universal Gravitation
Every particle in the universe attracts every other particle with a
force that is proportional to the product of their masses and
inversely proportional to the square of the distance between them.
This force acts along the line joining the two particles.
The magnitude of the gravitational force is given by
Where
and
are the masses of the two particles, is the
distance between them, and G is a gravitational constant.
Acceleration due to gravity at the surface of Earth
•
We substitute in the known values below
Earth
•
2RE
The value for the acceleration due to
gravity decreases as we move further from
the surface of the Earth.
RE
Newton’s Law of Universal
Gravitation
How do the gravities compare (assuming equal
masses)?
1. FA = FB
2. FA = 2 FB
3. FA = 4FB
4. 2 FA = FB
5. 4 FA = FB
Earth
A
B
2RE
RE
Newton’s law of gravity describes the gravitational force
between
A.
B.
C.
D.
E.
the earth and the moon.
a person and the earth.
the earth and the sun.
the sun and the planets.
all of the above.
A 60 kg person stands on each of the following planets. Rank
order her weight on the three bodies, from highest to lowest.
A.
B.
C.
D.
E.
A> B>C
B>A>C
B>C>A
C>B>A
C>A>B
Calculate the acceleration due to gravity on the Moon, which
has a radius of 1.74×106 m and a mass of 7.35×1022 kg.
Geosynchronous orbit
A satellite is in geosynchronous orbit. Geosynchronous orbit is when the
satellite orbits at a radius that allows the period of orbit to be 1 day (24 hrs).
- Remember that centripetal acceleration is
- The magnitude of the force is
which gives
- Newtons law of gravity is
- Determine the sum of the forces,
- The only acceleration is
, so
A
- We know the circumference of a circle and that
constant
velocity, therefore
is a
B
- Find the radius of orbit by plugging in B into A and solving for
radius of geosynchronous orbit,
where
gives the
According to Newton’s law of gravity, if the Earth’s
mass were suddenly doubled, with its distance
to the sun and its speed relative to the sun
unchanged, what would happen to its orbit?
1.
2.
3.
4.
It would fly off to the stars
It would spiral into the sun
It would just say ho hum (nothing changes).
We don’t know without more information.
A satellite orbits the earth. A Space Shuttle crew is sent to boost the
satellite into a higher orbit. Which of these quantities increases?
A.
B.
C.
D.
E.
Speed
Angular speed
Period
Centripetal acceleration
Gravitational force of the earth
The Moon does not fall to Earth because
A. It is in Earth’s gravitational field.
B. The net force on it is zero.
C. It is beyond the main pull of Earth’s gravity.
D. It is being pulled by the Sun and planets as well as
by Earth.
E. none of the above
F. all of the above
Kepler’s Laws
1.
The orbits of planets are
ellipses; and the center
of sun is at one focus
2.
The radius vector
sweeps out equal areas
in equal time
3.
The period T is
proportional to the mean
radius to the 3/2 power