Answer the following question.
What are (i) free fall, (ii) acceleration due to gravity (iii) escape velocity (iv) centripetal force?
Answers
Explanation:
(i) Free Fall: Whenever an object moves under the influence of the force of gravity alone, it is said to be in Free Fall. During free fall initial velocity of an object is zero and force of air also acts on an object. Thus real free fall is possible only in a vacuum because there is no air.
For Example:
a) When an object is dropped from the top of the table it falls down only due to gravitational force hence it is under free fall.
b) An apple falling from the tree.
But when we are standing on the ground, flying in a flight we are not in free fall because other forces except gravitational force are also acting.
(ii) Acceleration due to gravity: The acceleration which is gained by an object because of the gravitational force is called acceleration due to gravity. Its S.I unit is m/s2. It is denoted by ‘g’ and its value at the surface of the earth is 9.8m/s2.
It is a vector quantity (have both magnitude and direction) and it is directed towards the centre of the earth. The value of acceleration due to gravity is not fixed it changes from place to place Like at moon ‘g’ value is one-sixth of value on earth.
(iii) Escape velocity: The minimum value of the initial velocity at which an object to escape from the gravitational pull of the earth and never comes back to the earth is called the escape velocity.
The escape velocity from earth is about 11.186 km/s, means if an object travels 11.186 km in 1 sec it will escape from earth’s gravitational pull. All the satellites and rockets are launched with a velocity equal to escape velocity in order to escape from the earth’s gravity.
(iv) Centripetal force: The force that acts on an object to keep it moving along the circular path with constant speed is called the centripetal force.
It is given by Fc = mv²/r
It is directed towards the centre of the circle (of radius ‘r’) in which the object is moving ( with velocity ‘v’).
Example: The stone tied to a piece of string whirl in a circle due to centripetal force only.
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(i) In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it. In the context of general relativity, where gravitation is reduced to a space-time curvature, a body in free fall has no force acting on it.
(ii) The acceleration due to gravity is the acceleration produced in the freely falling body due to the influence of the gravitational pull of the earth. Acceleration due to gravity is denoted by ' g ' but its values vary. Like, for example, the acceleration due to gravity on the moon is different from that of the earth.
(iii) In physics, escape velocity is the minimum speed needed for a free, non-propelled object to escape from the gravitational influence of a massive body, that is, to achieve an infinite distance from it. Escape velocity is a function of the mass of the object and distance to the center of mass of the object.
(iv) a force that acts on a body moving in a circular path and is directed towards the centre around which the body is moving.
