Question

A satellite orbits the earth in a circle with constant speed. Which of the following is true? The net force on the satellite is zero because the satellite is not accelerating. The net force on the satellite is directed forward, in the direction of travel. The net force on the satellite is directed straight down, toward the Earth. The net force on the satellite is directed outward, away from the Earth.

Answer 1

Answer: The net force on the satellite is directed straight down, toward the Earth.

Step-by-step explanation:

A satellite orbiting the Earth is a characteristic example of the uniform circular motion, where the direction of the velocity vector
`\vec{V}` is perpendicular to the radius
`r` of the trajectory. Hence, the velocity is changing although the speed is constant.

On the other hand, acceleration
`\vec{a}` is directed toward the center of the circumference (that is why it is called centripetal acceleration).

Now, according to Newton's 2nd law, the force
`\vec{F}` is directly proportional and in the same direction as the acceleration:

`\vec{F}=m.\vec{a}`

Therefore, the net force on the satellite resulting from its circular motion points towards the center of the circle (where the Earth is in the Earth-satellite system).