PHYSICS: CHAPTER 2.5 NOTE PACKET
Chapter 2.5: Rockets and Satellites
I.
Vocabulary: Define the following terms from Chapter 2.4.
a. Satellite-any object that orbits another object in space.
b. Centripetal Force-Any force that causes an object to move in a circular path.
Chapter 2.5: Rockets and Satellites
II.
Notes:
a. Rockets and Satellites
i. HOW DO ROCKETS LIFT OFF?
1. Newton’s THIRD LAW(ACTION / REACTION)
a. Rocket pushes hot gases DOWN
b. Hot gases push rocket UP
i. UNBALANCED forces accelerate the rocket upward
1. Net Force = THRUST
ii. “A ROCKET CAN RISE INTO THE AIR BECAUSE THE GASES IT
EXPELS WITHA DOWNWARD ACTION FORCE EXERT AN EQUAL BUT
OPPOSITE REACTION FORCE ON THE ROCKET.”
iii. What is a Satellite?
1. ANY OBJECT THAT ORBITS ANOTHER OBJECT IN SPACE.
a. Natural: MOONS AND ASTEROIDS
b. Artificial: MAN-MADE OBJECTS
2. Circular Motion
a. Satellites follow an almost perfectly circular path around the Earth.
i. The FORCE that keeps an object in a circular path is
called a CENTRIPETAL FORCE:
1. GRAVITY is the centripetal force holding satellites
in orbit around the Earth.
2. TENSION is the centripetal force of a string
holding a ball moving in a circle.
3. FRICTION is the centripetal force of the road and
the tires of a car moving around a curve.
b. QUESTION: WHAT TYPE OF FORCE CAUSES AN OBJECT
TO MOVE IN A CIRCULAR PATH?
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3. SATELLITE MOTION
a. SATELLITES IN ORBIT AROUND EARTH
CONTINUOUSLY FALL TOWARD EARTH, but because
Earth is CURVED they travel around it.
i. Fig. 21, page 66.
4. SATELLITE LOCATION
a. Low Orbit
i. 400 km: SPACE SHUTTLE
ii. 1000 km: RESEARCH SATELLITES
b. High Orbit
i. 36,000 km: Communication satellites
1. GEOSYNCHRONOUS ORBIT
a. Orbiting Earth, but STAYING ABOVE
THE SAME LOCATION.
Chapter 2.5: Rockets and Satellites
III.
Assessment Questions
1.
Which of Newton’s three laws of motion explains how a rocket lifts off?
Newton’s third law of motion
2.
How do action-reaction pairs explain how a rocket lifts off?
A rocket can rise into the air because the gases it expels with a downward action force
exert an equal but opposite reaction force on the rocket.
3.
As a rocket travels upward from Earth, air resistance decreases along with the force of
gravity. The rocket’s mass also decreases as its fuel is used up. If thrust remains the same,
how do these factors affect the rocket’s acceleration?
All three factors increase the rockets acceleration. Decreased air resistance and force of
gravity allow the rocket to accelerate faster because both result in less force opposing the
rocket’s acceleration. Decreased rocket mass increases acceleration because the same force
is acting on a smaller mass.
4.
What is a satellite?
A satellite is an object that orbits another object in space.
5.
What causes satellites to stay in orbit rather than falling toward Earth?
Satellites stay in orbit because earth’s surface curves away as Earth’s gravity causes them to
fall toward earth.
6.
A projectile is thrown with enough velocity to orbit Earth. What would happen if the
projectile were thrown with a greater velocity?
If the projectile were thrown with a greater velocity, it would escape earth’s gravity and
move off into space.
7.
Draw a diagram showing the motion of a satellite around Earth. Label the forces acting
on the satellite. Is the satellite accelerating? Explain.
A satellite is accelerating towards the Earth due to the force of gravity.
A satellite does fall towards the Earth; only it never falls into the Earth because Earth is curved.