Question

Is this a true statement: If an object is weightless, then no gravity is acting upon it?

Answer 1

This is true.

Explanation:

Weight is the relation between mass and the planet's gravitational field. Weight is equal to the standard gravity multiplied by the mass of an object. For example, the Earth's gravitational field has a force of roughly 9.8 m/s^2. Therefore, someone who weighs 100 pounds on earth has a mass of about 10 kg. This means that gravity is necessary in order to have weight, and vice versa. Gravity causes weight. Therefore, an object that has no weight has no gravity acting upon it and the statement is true.

Answer 2

No. There is no such thing as weightlessness, except for energy, which is not matter.

Explanation:

There are no objects that are weightless. All objects have mass and take up space. Weight is the force of gravity acting on a body's mass and is determined by multiplying the mass times the acceleration due to gravity, which on earth is `-9.81"m/s"^2"`.

The reason an object seems to be weightless is because there is no contact force, such as normal force or friction acting on it. Gravity acts at a distance.

Gravity provides the centripetal force that keeps an object in orbit. Astronauts in orbit around the earth feel weightless because they are in constant free fall. The force of gravity keeps the space vehicle or international space station in orbit. However, since gravity acts at a distance, the astronauts feel weightless, when they actually are not. At the distance above the earth at which the shuttle and international space orbit, around `400` kilometers, the acceleration due to gravity is approximately `-8.7"m/s"^2"`.

http://www.physicsclassroom.com/class/circles/Lesson-4/Weightlessness-in-Orbit

http://www.nasa.gov/audience/forstudents/5-8/features/orbit_feature_5-8.html

http://hyperphysics.phy-astr.gsu.edu/hbase/orbv.html