Question

PHYSICS - SPOINTS
2. A cricket player holds a cricket ball of mass 100 g by moving his hands
backward by 0.75 m. If the
initial velocity of the ball is 108 kmh ', find the retarding force applied by the
player

Answer 1

Correct Question:

A cricket player holds a cricket ball of mass 100 g by moving his hands backward by 0.75 m. If the

initial velocity of the ball is 108 km/h, find the retarding force applied by the player.

Required Solution:

Given:

• Mass of the ball (m) = 100g = 0.1 kg
• Initial velocity (u) = 108 km/h = 30m/s
• Distance (s) = 0.75 m
• Final velocity (v) = 0m/s

To calculate:

• Regarding force applied by the player (a).

Calculation:

Firstly we'll calculate acceleration by the third equation of motion:

• 2as = v² - u²

→ 2 × a × 0.75 = (0)² - (30)²

→ 1.5a = 0 - 900

→ 1.5a = -900

→ a = 900/1.5

→ a = -600m/s²

Now, by using force formula:

• F = ma

→ F = 0.1 × (-600)

→ F = -60N ★

Therefore, regarding force applied by the player is -60N.

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More information!

Equations of motion:

• v = u + at
• s = ut + ½at²
• v² – u² = 2as

Where,

★ v = final velocity = m/s

★ u = initial velocity = m/s

★ a = acceleration = m/s²

★ s = distance/displacement = m

★ t = time = sec

Remember that!

• When a body starts from rest, its initial velocity is 0.

• When a body comes to stop or applies breaks, its final velocity is 0.

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Answer 2

It is know us that,

2ax = v² - u²

⇒ 2ax = - u²

⇒ a = - u²/2x

⇒ a = - (30)²/(2 · 0.75) m/s²

⇒ a = - 600 m/s²

And, F = ma

∴ F = (0.1 kg)(- 600 m/s²)

⇒ F = - 60 N (answer).

[Negative magnitude of force implies that the fielder gave a force equivalent to 60 N opposing the direction of the motion of the ball.]

More:-

Any physical quantity 'P' is given by,

P = nu

where n = magnitude/numerical value and u = unit. That's it.