Advertisements
Advertisements
प्रश्न
A metal ball of mass 5 kg falls from a height of 490 m. How much time it will take to reach the ground? (g = 9.8 m/s2)
Advertisements
उत्तर
Given, Mass (M) = 5 kg.
Distance travelled by the ball (s) = 490 m
Initial velocity of the ball (u) = 0
Gravitational acceleration (g) = 9.8 m/s2
Newton's second equation of motion gives
s = `"ut" + 1/2 "gt"^2`
∴ 490 = `0 xx "t" + 1/2 xx 9.8 xx "t"^2` .....[Initial velocity (u) = 0]
⇒ 490 = 4.9 t2
t2 = `490/4.9`
t2 = 100
t = 10 sec.
∴ The ball takes 10 seconds to reach the ground.
APPEARS IN
संबंधित प्रश्न
Gravitational force acts on all objects in proportion to their masses. Why then, a heavy object does not fall faster than a light object?
What force is responsible for the earth revolving round the sun ?
Fill in the following blank with suitable word :
The acceleration due to gravity on the moon is about ………………of that on the earth.
During a free fall, will heavier objects accelerate more than lighter ones ?
The values of g at six distances A, B, C, D, E and F from the surface of the earth are found to be 3.08 m/s2, 9.23 m/s2, 0.57 m/s2, 7.34 m/s2, 0.30 m/s2 and 1.49 m/s2, respectively.
(a) Arrange these values of g according to the increasing distances from the surface of the earth (keeping the value of g nearest to the surface of the earth first)
(b) If the value of distance F be 10000 km from the surface of the earth, state whether this distance is deep . inside the earth or high up in the sky. Give reason for your answer.
Why does a sharp knife cut objects more effectively than a blunt knife ?
Name the force which wears away two surfaces as they move over one another.
A pressure of 10 Pa acts on an area of 3.0 m2. What is the force acting on the area ? What force will be exerted by the application of same pressure if the area is made one-third ?
A force of 15 N acts on a body of mass 2 kg. Calculate the acceleration produced.
Figure shows the velocity-time graph of a particle of mass 100 g moving in a straight line. Calculate the force acting on the particle.
(Hint : Acceleration = Slope of the v-t graph)
What is the acceleration due to gravity?
In vacuum, all freely falling objects have the same force. Is it true?
Explain why:
Objects fall to the earth.
What do you understand by the free fall?
Right or wrong sentence:
The value of gravitational acceleration at the centre of earth is zero.
Write the acceleration due to gravity value on the surface of Earth.
Distinguish between:
Universal gravitational constant – Gravitational acceleration of earth.
The mass and weight of an object on earth are 5 kg and 49 N respectively. What will be their values on the moon? Assume that the acceleration due to gravity on the moon is 1/6th of that on the earth.
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?
When is free fall possible?
