Free Fall

Q.

If the value of $G$ (universal gravitational constant) is $6.67\times {10}^{-11}$ unit, then determine the value in CGS system.

Q.

The area under a $v–t$ graph represents a physical quantity that has the unit

1. $m^2$

2. $m$

3. $m^3$

4. $\frac{m}{s}$

Q.

If a ball is thrown vertically upwards with $40m/s$ its velocity after two seconds will be:-

Q.

Why at the centre of earth gravitational force is zero .is it because r=0 or the mass of earth at that point is zero?

Q. Derivation of s=ut+1/2(gt²

Q.

Why is G called the universal constant?

Q.

How does the value of ‘g’ change as one goes up above the surface of the earth?

Q.

Name the force which is holding the atmosphere to the earth.

Q.

A satellite of mass m revolves around the earth of radius R at a height x from its surface. If g is the acceleration due to gravity on the surface of the earth, the orbital speed of the satellite is

1. gx

2. $\frac{gR}{R-x}$

3. $\frac{g{R}^2}{R+x}$

4. ${\left(\frac{g{R}^2}{R+x}\right)}^{\frac{1}{2}}$

Q.

area under distance - time graph gives

Q.

In which of the following graphs are both runners moving at the same speed?

1. Graph-A

2. Graph-D

3. Graph-B

4. Graph-C

Q.

A stone is falling freely and describes a distance $S$ in $t$ seconds given by equation $S=\frac{1}{2}g{t}^2$. The acceleration of the stone is

1. Uniform

2. Zero

3. Non–uniform

4. Indeterminate

Q.

A body falls from a height of 500 m. In how much time, will it strike the ground ? (Give the answer in seconds)

Q.

The magnitude of gravitational force between the earth and 10 kg body is:

1. 98 N

2. 9.8 N

3. 90 N

4. 100 N

Q.

A uniform chain of length L and mass M is lying on a smooth table and one-third of its length is hanging vertically down over the edge of the table. If g is acceleration due to gravity, the work required to pull the hanging part on to the table is

1. 

2. 

3. 

4. 

Q.

Distance-time graph of two objects A and B are shown below.

Which statement is true for the speed of object A and B?

1. Speed of object A is greater than object B

2. Speed of object A is smaller than object B

3. Both have same speed

4. Speed of Object A is double the speed of object B.

Q.

Figure below shows the distance-time graph of three objects A, B and C. Find the speed of all the three bodies. Which of the following three is travelling the fastest? [3 MARKS]

Q. Starting from rest a car accelerates uniformly with 3meter per second square for 5sec and then moved with uniform velocity draw distance time graph of the motion of the car up to t=7sec

Q.

In the given velocity-time graph, AB shows that the body has

1. uniform acceleration

2. uniform retardation

3. uniform velocity throughout its motion and has zero initial velocity

4. none of these

Q.

If the ratio of the masses of two planets is 2:3 and the ratio of their radii is 4:7 then the inverse ratio of their acceleration due to gravity will be

1. 49:24

2. 24:49

3. 7:8

4. 8:7

Q.

Identical packets are dropped from two airplanes, one above the equator and the other 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.

The escape velocity of an object on a planet whose $g$ value is $9times$ on earth and whose radius is $4times$ that of the earth in km/s is

1. $67.2$

2. $33.6$

3. $16.8$

4. $25.2$

Q.

Write four phenomena that were successfully explained using the universal law of gravitation.

Q. A crumpled paper and a feather are dropped from the top of a building at the same time. Neglecting the air resistance, which one of them would reach the ground first?

1. Both would reach at the same time.
2. Data insufficient to determine
3. The feather
4. The crumpled paper

Q.

What do you mean by acceleration? How do you find acceleration from velocity-time graph?

Q.

Acceleration due to gravity of a body is independent of

1. mass of the body

2. altitude of the body

3. latitude of the body

4. depth below the earths surface

Q. 1. Write the three equation of motion for freely falling bodies and write the value of g.

2. A cricket ball is dropped from a height of 20 metres. [5 MARKS]

(a) Calculate the speed of the ball when it hits the ground

(b) Calculate the time it takes to fall through this height.

Q.

Identify free fall situations from the following.

1. A man landing with a parachute.

2. An apple falling on the Moon.

3. A rocket propelling into space.

4. A block falling from a cliff.

Q. While playing, Ria's brother Vedant throws a ball upwards with a speed of $20m/s$ . Find the total time of a ball in the air, take acceleration due to gravity, $g=10m{s}^{-2}$

1. 8 seconds
2. 4 seconds
3. 6 seconds
4. 2 seconds

Q.

Distance-time graph of two objects A and B are shown below.

1. Speed of object A is smaller than object B

2. Speed of object A is greater than object B

3. Speed of Object A is double the speed of object B.

4. Both have same speed