Advertisements
Advertisements
प्रश्न
Write scientific reasons.
The value of gravitational acceleration (g) is taken to be -g when studying the motion of an object thrown upwards in a straight line.
Advertisements
उत्तर
- For the motion of an object thrown upwards, the magnitude of g is the same throughout the motion, but the velocity of the object decreases with the increase in height.
- For an object thrown upwards, the direction of acceleration due to gravity is opposite to the velocity of the object.
Hence, the value of gravitational acceleration (g) is taken to be -g when studying the motion of an object thrown upwards in a straight line.
APPEARS IN
संबंधित प्रश्न
What do you mean by free fall?
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement and the total distance covered by the stone?
What is the acceleration produced in a freely falling body of mass 10 kg ? (Neglect air resistance)
What force is responsible for the earth revolving round the sun ?
Explain why, if a stone held in our hand is released, it falls towards the earth.
Explain why, a wide steel belt is provided over the wheels of an army tank.
A stone is thrown vertically upwards with initial velocity u reaches a height ‘h’ before coming down. Show that the time taken to go up is the same as the time taken to come down.
What would be the value of ‘g’ on the surface of the earth if its mass was twice and its radius half of what it is now?
A force of 15 N acts on a body of mass 2 kg. Calculate the acceleration produced.
A car is moving with a uniform velocity 30 ms-1. It is stopped in 2 s by applying a force of 1500 N through its brakes. Calculate the following values : The retardation produced in car.
Define the term acceleration due to gravity? Write its S.I. unit.
How are g and G realated ?
A body falls freely under gravity from rest and reaches the ground in time t. Write the expression for the height fallen by the body.
In vacuum, all freely falling objects have the same force. Is it true?
What do you understand by the free fall?
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. |
- 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.
- Why does free fall not happen on the earth?
- Why does the velocity of the object increase during the free fall?
- Which type of force exerts on the object during free fall?
- Why does free fall happen only in a vacuum?
Calculate the escape velocity on the surface of the moon given the mass and radius of the moon to be 7.34 × 1022 kg and 1.74 × 106 m respectively.
(Given: G = 6.67 × 10-11 Nm2/kg2)
