PHYSICS: CHAPTER 2.5 NOTE PACKET
Chapter 2.5: Rockets and Satellites
Vocabulary: Define the following terms from Chapter 2.4.
Satellite-any object that orbits another object in space.
Centripetal Force-Any force that causes an object to move in a circular path.
Chapter 2.5: Rockets and Satellites
Notes:
Rockets and Satellites
HOW DO ROCKETS LIFT OFF?
Newton’s THIRD LAW(ACTION / REACTION)
Rocket pushes hot gases DOWN
Hot gases push rocket UP
UNBALANCED forces accelerate the rocket upward
Net Force = THRUST
“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.”
What is a Satellite?
ANY OBJECT THAT ORBITS ANOTHER OBJECT IN SPACE.
Natural: MOONS AND ASTEROIDS
Artificial: MAN-MADE OBJECTS
Circular Motion
Satellites follow an almost perfectly circular path around the Earth.
The FORCE that keeps an object in a circular path is called a CENTRIPETAL FORCE:
GRAVITY is the centripetal force holding satellites in orbit around the Earth.
TENSION is the centripetal force of a string holding a ball moving in a circle.
FRICTION is the centripetal force of the road and the tires of a car moving around a curve.
QUESTION: WHAT TYPE OF FORCE CAUSES AN OBJECT TO MOVE IN A CIRCULAR PATH? ________________________________________________
SATELLITE MOTION
SATELLITES IN ORBIT AROUND EARTH CONTINUOUSLY FALL TOWARD EARTH, but because Earth is CURVED they travel around it.
Fig. 21, page 66.
SATELLITE LOCATION
Low Orbit
400 km: SPACE SHUTTLE
1000 km: RESEARCH SATELLITES
High Orbit
36,000 km: Communication satellites
GEOSYNCHRONOUS ORBIT
Orbiting Earth, but STAYING ABOVE THE SAME LOCATION.
Chapter 2.5: Rockets and Satellites
Assessment Questions
Which of Newton’s three laws of motion explains how a rocket lifts off?
Newton’s third law of motion
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.
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?
Newton's 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.
What is a satellite?
A satellite is an object that orbits another object in space.
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.
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.
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.
2 SOLID STATE PHYSICS (INDIA) 45 (2002) XXXXXY PROCEEDINGS
20TH GAMOW INTERNATIONAL ASTRONOMICAL CONFERENCESCHOOL ASTRONOMY AND BEYOND ASTROPHYSICS
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