Tag: gravitation: planets and satellites

Quizzes (6) Questions (38)

Questions Related to gravitation: planets and satellites

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

The time period of a second's pendulum inside a satellite will be

  1. zero
  2. $1$ sec
  3. $2$ sec

  4. infinite
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

time period $\propto \sqrt { \cfrac { l }{ g }  } $ , as in the satellite there will be no gravity so the time period will be infinite.(logical explanation. : without gravity there will be no force on pendulum so it will not move a bit even in infinite time.)

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

In an earth satellite moving in a circular orbit, a piece of metal weighing $16g$ (on the earth) is weighed by a spring balance while the metal is suspended in water. If the relative density of the metal is $8$, what weight will be recorded?

  1. $-2$ g

  2. zero
  3. $2$ g
  4. $14$ g
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the satellite the spring is in free fall so no weight will be recorded.

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

The radius and mean density of the earth are $R$ & $p$ respectively . the critical orbital speed of a satellite for a low altitude orbit is 

  1. $ 2 \sqrt {\dfrac { \pi G p}{3R}} $
  2. $ 2R \sqrt {\dfrac { \pi Gp}{3}} $
  3. $ 2R \sqrt {\dfrac {2 \pi G p}{3}} $
  4. $ 2R \sqrt {\dfrac { \pi Gp}{2}} $
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Orbital speed v = sqrt(GM/R). Mass M = density * volume = p * (4/3) * pi * R^3. Substituting M: v = sqrt(G * p * 4/3 * pi * R^3 / R) = sqrt(4/3 * pi * G * p * R^2) = 2R * sqrt(pi * G * p / 3).

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

An astronaut, inside an earth satellite, experiences weightlessness because

  1. no external force is acting on him

  2. he is falling freely

  3. no reaction is exerted by the floor of the satellite

  4. he is far away from the earth's surface
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

For an earth satellite moving in a circular orbit, centripetal force required for its circular motion is provided by the gravitational force exerted by earth on it.
 It means resultant force on the astronaut is equal to the gravitational force exerted by earth on him. Hence, no reaction is exerted by floor of the satellite on him.
In other words, his acceleration towards earth centre (centripetal acceleration) is exactly equal to acceleration caused by the gravitational force alone.
Hence, options (b) and (c) are correct.

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

Weightlessness experienced while orbiting the earth in a spaceship is the result of

  1. Inertia

  2. Accelaration

  3. Zero gravity

  4. Centre of gravity
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Weightlessness means that there is no reaction on a body from the floor. Since both the artificial satellite & the astronaut have same centripetal acceleration (as in a lift; which is falling freely, we does not feel any weight, because both lift & we fall with same acceleration). so the astronaut does not feel any weight inside the space craft

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

A body suspended from a spring balance is placed in a satellite. Reading in balance is $W _1$ when the satellite moves in an orbit of radius $R$. Reading in balance is $W _2$ when the satellite moves in an or bit of radius $2R.$ Then.

  1. $W _1 = W _2$
  2. $W _1 > W _2$
  3. $W _1 < W _2$
  4. $W _1 =2 W _2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since,Both the satellites are freely falling bodies.
so,$W _1=W _2$

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

Moon is a satellite of the Earth, but weightlessness is not experienced at the surface of the Moon because

  1. its distance from the Earth is more.

  2. it is a natural satellite.

  3. its size is big but density is very low.

  4. its own mass is more.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

As Moon has its mass, thus it posses its own gravity ($\frac {1}{6}$th of that of the Earth). Hence, weightlessness is not experienced at the surface of the Moon.

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

Weightlessness experienced in a spaceship is due to

  1. absence of of inertia.

  2. absence of gravity.

  3. absence of accelerating force.

  4. free fall of the spaceship.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

It is a misconception that there is no gravity in space.
An astronaut experiences weightlessness due the fact that as the spacecraft revolves around the Earth, the astronaut is continuously falling towards the Earth. This is similar to what a person standing in an elevator, that is falling freely, would experience. The person would be weightless as the elevator falls.

Multiple choice physics gravitation: planets and satellites weightlessness application of newton's law of motion escape velocity

Read the assertion and reason carefully to mark the correct option out of the options given below :

Assertion : An astronaut in a satellite feels weightlessness.
Reason : As observed by another astronauts in the same satellite, force of gravity and centrifugal force balance each other.

  1. If both assertion and reason are true and the
    reason is the correct explanation of the assertion

  2. If both assertion and reason are true but reason
    is not the correct explanation of the assertion

  3. If assertion is true but reason is false

  4. If assertion is false but reason is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

In a satellite, weightlessness is felt.

The weight of a person in a satellite is balanced by the centrifugal force due to orbiting of the satellite around the earth, i.e.,
$mg=\dfrac{mv^2}{r}$