# Class 11 Physics MCQ – Gravitation – Weightlessness

This set of Class 11 Physics Chapter 8 Multiple Choice Questions & Answers (MCQs) focuses on “Gravitation – Weightlessness”.

1. For an object experiencing weightlessness _____
a) its weight force is non-zero
b) it has inertia
c) it experiences a value of acceleration greater than the acceleration due to gravity
d) it experiences a value of acceleration lesser than the acceleration due to gravity

Explanation: Since the object has mass, it always has inertia. However, weight force is zero and hence the experienced acceleration is zero because it is experiencing weightlessness.

2. Why do the astronauts in the international space station experience weightlessness?
a) The acceleration due to gravity at that height is zero
b) They are falling towards the earth
c) They have specially designed spacesuits for this purpose
d) The gravity of the moon and earth cancel out at that altitude

Explanation: The parabolic trajectory of the free fall of the international space station is at such high velocity that it essentially orbits the planet. The weightlessness experienced by the astronauts in the ISS is the consequence of this freefall.

3. An object is weightless inside a uniform spherical shell.
a) True
b) False

Explanation: The net acceleration due to gravity is zero at all points inside a uniform spherical shell because of which an object is weightless. This is because the sum of gravitational force vectors from all sides of the object is zero inside the shell.

4. A person sitting in a chair in a satellite feels weightless because _____
a) the earth does not attract the objects in a satellite
b) the normal force by the chair on the person balances the earth’s attraction
c) the normal force is zero
d) the person in the satellite is not accelerated

Explanation: Since the person sitting in the chair in the satellite is essentially in freefall along with the satellite, he does not experience any reaction force. The lack of reaction force (or) normal force makes a person feel weightless.

5. How do astronauts define “up” or “down” in space?
a) There is no “up” or “down” in space
b) The side facing the earth is “down” and the opposite side is ‘up”
c) “up’ or “down” is decided by the control centre on earth
d) The direction of the spacecraft’s power source is “up” and the opposite side is “down”

Explanation: There is no “up” or “down” in space due to the lack of normal reaction forces for their weights. Gravity defines the vertical direction. Thus for the astronauts, all directions are the same.
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Sanfoundry Global Education & Learning Series – Physics – Class 11.

To practice all chapters and topics of class 11 Physics, here is complete set of 1000+ Multiple Choice Questions and Answers.