Gravitational Force

Q. The count rate of a Geiger- Muller counter for the radiation of a radioactive material of half life of 30 minutes decreases to $5s^{-1}$ after 2 hours. The initial count rate was

1. $25s^{-1}$
2. $625s^{-1}$
3. $20s^{-1}$
4. $80s^{-1}$

Q.

Find the gravitational force between earth and moon given that mass of earth = $6\times {10}^{24}\mathrm{kg}$, mass of moon = $7.2\times {10}^{22}\mathrm{kg}$ and the center to center distance of earth and moon = $3.84\times {10}^8\mathrm{m}$.

Q.

What are the units of gravity in S.I.?

Q.

Define the force of gravitation and give some examples of it.

Q.

the gravitational force between two point masses $m_1$ and $m_2$ at separation, r is given by

$F=k\frac{m_1{m}_2}{r^2}$
The constant k:
1. Depends on the system of units only

2. Depends on the medium between masses only
3. Depends on both (1) and(2)
4. Is independent of both (1) and (2)

Q. Why are high tides higher than normal days on a new moon or full moon?

1. The moon is closer to Earth on new moon and full moon
2. The moon is closer to the sun on new moon and full moon
3. Very high tides are caused when Earth, Moon and Sun are all aligned in a straight line, which happens on a new moon or full moon
4. Earth is closer to the sun on new moon and full moon

Q. According to Snell’s law, sin i/sin r is equal to of the second medium with respect to the first medium.

1. reflective index
2. frequency index
3. refractive index

Q.

Statement 1: Tides are periodic rise and fall of the ocean's surface.
Statement 2: Tides are caused by combined effects of the gravitational forces exerted by the Moon and the Sun.
Choose the correct option.

1. Both the statements are correct.

2. Both the statements are incorrect.

3. Statement 1 is correct but statement 2 is incorrect.

4. Statement 2 is correct but statement 1 is incorrect.

Q.

The distance of separation between two bodies affects the magnitude of the non-contact force between them such that

1. Magnitude of non-contact forces are inversely proportional to the distance between the 2 bodies

2. Magnitude of non-contact forces are directly proportional to the square of distances between the 2 bodies

3. Magnitude of non-contact forces are inversely proportional to the square of distances between the 2 bodies

4. Magnitude of non-contact forces are directly proportional to the distance between the 2 bodies

Q.

A solid sphere of uniform density and radius 4 units is located with its centre at the origin O. Two spheres of equal radii 1 unit, with their centres at A (- 2, 0, 0) and B (2, 0, 0) respectively are taken out of the solid leaving behind spherical cavities as shown in the figure. Then choose the incorrect statement.

1. The gravitational force due to this object at the origin is zero.

2. The gravitational force at point B (2, 0, 0) is zero.

3. The gravitational potential is the same at all points of the circle $y^2+z^2=36$.

4. The gravitational potential is the same at all points of the circle $y^2+z^2=4$.

Q.

What is the difference between gravity and gravitation?

Q.

The gravitational force between two bodies varies with distance $r$ as:

1. $1/r$

2. $1/r^2$

3. $r$

4. $r^2$

Q.

A sphere of mass $40kg$ is attracted by another sphere of mass $15kg$ with a force of $\frac{1}{10}mgwt$. Find the constant of gravitation if the centres of the spheres are $0.2m$apart.

Q.

Classify the following amongst the contact and non-contact forces:

i) frictional force,

ii) normal reaction force

iii) force of tension in a string,

iv) gravitational force

1. Contact force: force of tension in a string

   Non-contact force: gravitational force, frictional force, normal reaction force

2. Contact force: frictional force, normal reaction force, force of tension in a string

   Non-contact force: gravitational force

3. Contact force: frictional force, force of tension in a string

   Non-contact force: gravitational force, normal reaction force

4. Contact force: frictional force, normal reaction force

   Non-contact force: gravitational force, force of tension in a string

Q.

Derive the relationship F = ma, where each symbol has its usual significance.

Q.

The Centres Of Two Identical Spheres Are $1m$ Apart If The Gravitational Force Between The spheres be $1N$, then what is the mass of each sphere? ($G=6.67\times {10}^{-11}N{m}^2/k{g}^2$)

Q. Suppose the gravitational force between two spheres is $30N$. If the magnitude of each mass doubles, what is the force between the masses?

1. $80N$
2. $150N$
3. $300N$
4. $120N$

Q.

Why do all objects have a tendency to fall towards the Earth when thrown up?

Q.

Two balls are thrown simultaneously in air. The acceleration of the centre of mass of the two balls, while in air

Q.

Determine the gravitational force of interaction between two spheres of masses 20 kg and 50 kg and radii 3 m and 2 m, respectively. The separation between their centers is 10 m.

Q.

Two particles are placed at some distance. If the mass of each of the two particles is doubled, keeping the distance between them unchanged, the value of gravitational force between them will be

1. 14 times

2. 2 times

3. 4 times

4. Unchanged

Q.

Gravitational force is non-conservative.

1. True
2. False

Q. How to calculate force of electrostatic when there two mediums other than air

Q. A person is pushing a box kept on a rough surface as shown below. Identify the force types P, Q and R acting on the box.

1. P - Muscular force, Q - Gravitational force, R - Frictional force
2. P - Muscular force, Q - Frictional force, R - Gravitational force
3. P - Gravitational force, Q - Frictional force, R - Muscular force
4. P - Frictional force, Q - Gravitational force, R - Muscular force

Q.

What is contact and non-contact forces?​​​​​​

Q.

The force required to move a mass of $1kg$ at rest on a horizontal rough plane ($\mu =0.1$and$g=9.8m{s}^{-2}$) is

1. $0.98N$

2. $0.49N$

3. $9.8N$

4. $4.9N$

Q.

Is gravity a force?

Q. Why induction does not takes place in particles?

Q.

Suppose the gravitational force varies inversely as the nth power of distance. Then the time period of a planet in circular orbit of radius R around the sun will be proportional to:

1. $R^{\left(\frac{n+1}{2}\right)}$

2. $R^{\left(\frac{n-1}{2}\right)}$

3. $R^n$

4. $R^{\left(\frac{n-2}{2}\right)}$

Q. The force of gravity on you is greatest when you are _____.

1. far above Earth's surface
2. just above Earth's surface
3. on Earth's surface
4. at centre of the earth