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Question

A boy throws two balls in air in such a manner that when the first ball is at its maximum height he throws the second ball. If the balls are thrown with the time difference of one second, the maximum height attained by each ball is \((g = 10 \text{ m/s}^2)\)

This question was previously asked in
RRB ALP 2018 CBT 2 Fitter Question Paper (21-Jan-2019) (Shift 3)
The correct answer is
5 m

Physics Problem: Maximum Height Calculation

This problem involves calculating the maximum height (\(H\)) reached by balls thrown vertically upwards under gravity (\(g\)). We need to use concepts from kinematics.

Analyzing the Conditions

  • The second ball is thrown exactly when the first ball reaches its maximum height.
  • The time difference between the throws of the two balls is given as 1 second.
  • Acceleration due to gravity, \(g = 10 \text{ m/s}^2\).

Combining these two conditions, we infer that the time taken for the first ball to reach its maximum height is exactly 1 second. Let this time be \(t_{max}\).

So, \(t_{max} = 1 \text{ s}\).

Calculating Initial Velocity

For an object thrown vertically upwards, the velocity (\(v\)) at time (\(t\)) is given by \(v = u - gt\), where \(u\) is the initial velocity.

At the maximum height, the final velocity \(v = 0\). Therefore:

\(0 = u - g t_{max}\)

\(u = g t_{max}\)

Substituting the values:

\(u = (10 \text{ m/s}^2) \times (1 \text{ s})\)

\(u = 10 \text{ m/s}\)

This is the initial velocity with which the balls are thrown.

Calculating Maximum Height

The maximum height (\(H\)) reached by a projectile can be calculated using the formula:

\(H = \frac{u^2}{2g}\)

Substituting the calculated initial velocity (\(u = 10 \text{ m/s}\)) and the given value of \(g\):

\(H = \frac{(10 \text{ m/s})^2}{2 \times (10 \text{ m/s}^2)}\)

\(H = \frac{100 \text{ m}^2/\text{s}^2}{20 \text{ m/s}^2}\)

\(H = 5 \text{ m}\)

Since both balls are thrown under the same conditions (implied), they will attain the same maximum height.

Conclusion

The maximum height attained by each ball is 5 m.

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Similar Questions

  1. The value of g on the moon is 1/6 th of the value of g on the earth. If a man can jump 1.5 m high on the earth, on the moon, he can jump up to a height of:

  2. Fill in the blank with the most appropriate option.

    The Universal Constant of Gravitation is ________.

  3. Consider a hypothetical planet whose mass and radius are both half that of Earth. If g is the acceleration due to gravity on the surface of Earth, the acceleration due to gravity on the planet will be:

  4. Let \(W_e\) and \(W_m\) be the weight of an object on the Earth and the Moon, respectively. Then, the ratio \(W_e/W_m\) is equal to ______.
  5. Two spheres of masses \(m\) and \(M\) are situated in air and the gravitational force between them is \(F\). The space between the masses is now filled with a liquid of specific gravity 3. The gravitational force will now be:
  6. An object with a specific mass will weigh ______.
  7. What will happen during the free fall of a massive object under the influence of gravitational force of the earth ?

  8. Which of the following statements is/are INCORRECT?

    A. The ratio of the force of gravitation between two masses, m1 and m2, kept at a distance R on the earth and on the moon is 1:1.
    B. Nm2/kg2 is the SI unit of G.
    C. The value of G depends on the distance between the bodies.
    D. The value of G depends on the masses of the bodies.
  9. Acceleration due to gravity is highest at ____.

  10. A 100 gram ball is kept on the top of a building of 70 m height. Find the potential energy of the ball (assume g = 10 m/s 2)


Important Questions from Gravity

  1. Which of the following statement is correct?

    I. Gravitation is a weak force unless large masses are involved.

    II. The weight is equal to the product of mass and acceleration due to gravity.

  2. What is the reason that the value of g (acceleration due to gravity) becomes greater at the poles than at the equator?

  3. If the acceleration due to gravity on the surface of earth is g, then the acceleration due to gravity on the surface of a planet whose mass is same as that of earth and radius is twice as that of earth is ___________.

  4. A man's mass is 72 kg on the earth. His mass on the moon will be:

  5. At which of the following place, weight of an object is maximum?

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