Free Fall

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. $R^n$

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

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

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

Q.

Why does an astronaut feel weightlessness in a satellite?

Q.

The acceleration due to gravity decreases with increase in altitude from the surface of the earth. State true or false.

1. True
2. False

Q.

A body is said to be in translational equilibrium when___.

1. the overall acceleration is zero

2. the overall acceleration is maximum

3. the overall velocity is maximum

4. the sum of all masses is zero

Q. Question 17
A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet.

Q.

What is the work done by the force of gravity on a satellite moving around the earth? Justify your solution.

Q.

If the mass of a body is 5kg, its weight on the surface of the earth would be ___ N (newton). $(g=9.8m/s^2)$

Q.

What is the value of the acceleration due to gravity at the center of the Earth?

1. Can not be determined
2. 0 m/s ${}^2$
3. Greater than that at surface
4. Infinite

Q. Question 13
Suppose a ball of mass m is thrown vertically upward with an initial speed, v its speed decreases continuously till it becomes zero. Thereafter, the ball begins to fall downward and attains the speed vagain before striking the ground. It implies that the magnitude of initial and final momentum of the ball is same. Yet, it is not an example of conservation of momentum. Explain why?

Q.

What is the value of G in S.I. unit?

Q. Small steel balls fall from rest through the opening at a steady rate of 2 balls per second. The vertical separation h of two balls when the lower one has dropped 20 meter is?

Q.

A baseball is popped straight up into the air and has a hang-time of 6 s. Determine the maximum height to which the ball rises.

1. 22.5 m

2. 90 m

3. 45 m

4. 180 m

Q. Calculate the pressure developed by a force of $\text{50 N}$ acting on an area of ${\text{10 m}}^2$.

1. $\text{10 Pa}$
2. $\text{5 Pa}$
3. $\text{15 Pa}$
4. $\text{20 Pa}$

Q.

If heavier bodies are attracted more strongly by the earth, why do they not fall faster to the ground?

Q. The value of $g$ at a particular point on the earth surface is $9.8m{s}^{-2}$. Suppose the earth suddenly shrinks uniformly to half its present size without losing any mass. The value of ‘g’ at the same point (assuming that the distance of the point from the centre of earth does not shrink) will now be:

1. $9.8m{s}^{-2}$
2. $4.9m{s}^{-2}$
3. $19.6m{s}^{-2}$
4. $3.1m{s}^{-2}$

Q. What is the minimum velocity needed for a spaceship to escape the Earth's gravitational force?

1. $5.4{\text{km s}}^{-1}$
2. $8.6{\text{km s}}^{-1}$
3. $11.2{\text{km s}}^{-1}$
4. $9.8{\text{km s}}^{-1}$

Q. An object thrown vertically upwards reaches a height of $500m$. What was its initial velocity? How long will the object take to come back to the earth? Assume $g=10m{s}^{-2}$.

1. $50m{s}^{-1}$ and $5s$
2. $100m{s}^{-1}$ and $20s$
3. $200m{s}^{-1}$ and $40s$
4. $300m{s}^{-1}$ and $30s$

Q. If the mass of a body is $5kg$, its weight on the surface of Earth would be: (Take $g=9.8m{s}^{-2}$)

1. $60N$
2. $70N$
3. $49N$
4. 
   $50N$

Q.

An astronaut orbiting the earth in a circular orbit 120 km above the surface of the earth, gently drops a spoon out of the spaceship. The spoon is likely to:

1. Move towards the moon
2. Will move along with space-ship
3. Will move in an irregular way then fall down to earth
4. Fall vertically down to the earth

Q.

A ball is dropped, at t = 0, from a certain height above the ground, At t=1s another ball is dropped from the same height. the distance between the two balls at t = 3s is (take g= 10 meters per second).

1. 5m

2. 20m

3. 25m

4. 125m

Q.

The two bodies (particles) are moving under their mutual gravitational interaction (assume no other force is acting on them), then the total work done on the two bodies in a particular time interval

1. is always zero

2. is always positive

3. is always negative

4. can be zero sometimes

Q.

A person standing on the edge of a cliff at some height above the ground throws the first ball straight up with an initial velocity u and then throws the second ball straight down with the same initial velocity u. Which of the following statements is TRUE regarding their velocities when they hit the ground?

1. Can’t say as final velocity depends on other factors as well.

2. Second ball will have higher velocity than the first.

3. Both the balls will have the same velocity when they hit the ground.

4. First ball will have higher velocity than the second.

Q.

A body of mass 1 kg is thrown vertically up with an initial speed of 15 ms-1. What is the magnitude and direction of the force due to gravity acting on the body when it is at the highest point ?

1. 19.6 N directed downwards
2. 9.8 ${\text{m/s}}^2$directed downwards
3. 9.8 m/s directed downwards
4. 9.8 N directed downwards

Q. An object is dropped from a height of $5m$ and it takes $5s$ to reach the ground. Calculate the acceleration due to gravity at that place.

1. $0.1m{s}^{-2}$
2. $0.2m{s}^{-2}$
3. $0.3m{s}^{-2}$
4. $0.4m{s}^{-2}$

Q. Question 2
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?

Q.

With respect to a satellite going around the earth in an orbit, which of the following statements is wrong?

1. It is moving with a constant speed
2. Its angular momentum remains constant
3. It suffers no acceleration
4. It is a freely falling body

Q. Find the dimension of force in terms of density ;acceleration due to gravity g; frequency

Q.

Identical packets are dropped from two airplanes, one above the equator and another above the North Pole, both at height ‘h’. Assuming all conditions are identical, will those packets take the same time to reach the surface of the earth. Justify your answer.

Q. Gravitational force acts on all objects in proportion to their masses. Why then, a heavy objects does not fall faster than a light object?

Q.

When a body is deformed, its centre of gravity

1. Does not Change

2. Changes

3. Moves upwards

4. Moves downwards