Advertisements
Advertisements
Question
A stone is released from the top of a tower of height 19.6 m. Calculate its final velocity just before touching the ground.
Solution
Initial velocity, u = 0 m s-1
Final velocity, v =?
Height of the tower, h = 19.6 m
Acceleration due to gravity, g = 9.8 m s-2
Using the equation, v2 - u2 = 2gs = 2gh
v2 - 0 = 2 × 9.8 m s-2 × 19.6 m
v2 = 19.6 m s-2 × 19.6 m
v2 = (19.6)2 m2 s-2
or v = 19.6 m s-1
APPEARS IN
RELATED QUESTIONS
What do you mean by acceleration due to gravity?
What is the acceleration produced in a freely falling body of mass 10 kg ? (Neglect air resistance)
State whether the following statement is true or false :
The acceleration due to gravity acting on a freely falling body is directly proportional to the mass of the body.
Name the force which pulled the apple off Isaac Newton’s tree.
A force acts for 0.1 s on a body of mass 2.0 kg initially at rest. The force is then withdrawn and the body moves with a velocity of 2 m s-1. Find the magnitude of the force.
What do you understand by the free fall?
Define acceleration due to gravity.
Write acceleration due to gravity value on the surface of Earth.
Write a short note.
Escape Velocity
Read the given passage carefully and answer the questions.
We know that the force of gravity due to the earth acts on each and every object. When we were holding the stone in our hand, the stone was experiencing this force, but it was balanced by a force that we were applying on it in the opposite direction. As a result, the stone remained at rest. Once we release the stone from our hands, the only force that acts on it is the gravitational force of the earth and the stone falls down under its influence. Whenever an object moves under the influence of the force of gravity alone, it is said to be falling freely. Thus the released stone is in a free fall. In free fall, the initial velocity of the object is zero and goes on increasing due to the acceleration due to the gravity of the earth. During free fall, the frictional force due to air opposes the motion of the object and a buoyant force also acts on the object. Thus, true free fall is possible only in a vacuum.
1) Complete the following statement by choosing the right option.
The stone held in the hand is stable because on it __.
- two unbalanced forces are exerted.
- only the gravitational force of the earth is exerted.
- gravitational force of the earth is not exerted.
- two balanced forces are exerted.
2) Why does free fall not happen on the earth?
3) Why does the velocity of the object increase during the free fall?
4) Which type of force exerts on the object during free fall?
5) Why does free fall happen only in a vacuum?
