Physics ch 10

Why doesn't the force of gravity change the speed of a satellite in circular orbit?

The speed of the satellite doesn't change because there is no component of gravitational force in the direction of its motion.

A projectile is launched vertically at 100 m/s. If air resistance can be ignored, at what speed will it return to its initial level?

100 m/s

A certain satellite has a kinetic energy of 8 billion joules at perigee (The point closest to earth) and 5 billion joules at apogee(Point farthest from earth). As the satellite travels from apogee to Parigi, how much work does the gravitational force due on it? Does its potential energy increase or decrease during this time, and by how much?

3,000,000,000 J of work was done by the gravitational force. When traveling from the apogee to perigee, the gravitational force does 3,000,000,000 J of work. When traveling from the apogee to perigee, the Potential energy decreases by 3 billion joules(on this path, the gravitational force is converting 3,000,000,000 J of energy from potential energy to kinetic energy)

A projectile is launched upward at an angle of 70° from the horizontal and strikes the ground a certain distance down range. For what other angle of launch at the same speed will this projectile Land just as far away?

An angle of 15° with produce the same range.

Is the sum of kinetic and potential energy a constant for satellites in circular orbits, in elliptical orbits, or in both?

KE+PE is constant during elliptical and circular orbits.

Why is Kenetic Energy a constant for a satellite in a circular orbit but not for a satellite in an elliptical orbit?

The Kenetic Energy is constant in a circular orbit because no work is done by gravity on the satellite.

At what part of an elliptical orbit doesn't earth satellite have the greatest speed? The lowest speed?

The satellite has its greatest speed when its nearest the earth, and its lowest speed when it's farthest away from the earth.

Why does the vertical component of velocity for a projectile change with time, whereas the horizontal component of velocity doesn't change?

The vertical component changes because vertical motion is influenced by the gravitational force (which acts in the vertical direction). The horizontal component of velocity doesn't change because the gravitational force is perpendicular to this component(not along it). And therefore can't influence it. (A force needs to have a component along the motion in order to influence that motion)

A stone is thrown upward at an angle. What happens to the vertical component of its velocity as it rises? As it falls?

The vertical speed/velocity will slow as it rises, and it will increase as it falls.

At a particular point in its orbit, a satellite in an elliptical orbit has a gravitational potential energy of 5000 MJ with respect to earths surface and a Kinetic energy of 4500 MJ. Later in its orbit, the satellites potential energy is 6000 MJ. What is its kinetic energy at that point?

Total energy= 5000MJ +4500MJ=9000MJ 9000MJ-6000MJ= 3500MJ KE= 3500MJ

Why does the force of gravity change the speed of a satellite in an elliptical orbit?

When a satellite is in an elliptical orbit, the gravitational force will have a component along the direction of motion at all points of the orbit, except for the perigee and apogee.

The stone is thrown upward at an angle. What happens to the horizontal component of its velocity as it rises? As it falls?

With no air resistance the horizontal component of velocity will remain constant, both in rising and falling.