A 1 kg ball is dropped from a height of 20 m. What is its velocity just before i

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Question: A 1 kg ball is dropped from a height of 20 m. What is its velocity just before it hits the ground? (g = 10 m/s²) (2021)

Options:

Correct Answer: 20 m/s

Exam Year: 2021

Solution:

Using the formula v = √(2gh) = √(2 × 10 m/s² × 20 m) = √400 = 20 m/s.

A 1 kg ball is dropped from a height of 20 m. What is its velocity just before it hits the ground? (g = 10 m/s²) (2021)

A 1 kg ball is dropped from a height of 20 m. What is its velocity just before it hits the ground? (g = 10 m/s²) (2021)

Step 1: Identify the given values. The mass of the ball is 1 kg, the height from which it is dropped is 20 m, and the acceleration due to gravity (g) is 10 m/s².
Step 2: Use the formula for velocity just before hitting the ground, which is v = √(2gh).
Step 3: Substitute the values into the formula: v = √(2 × 10 m/s² × 20 m).
Step 4: Calculate the value inside the square root: 2 × 10 m/s² = 20 m/s², then 20 m/s² × 20 m = 400 m²/s².
Step 5: Take the square root of 400 m²/s²: √400 = 20 m/s.
Step 6: Conclude that the velocity of the ball just before it hits the ground is 20 m/s.

Kinematics – The question tests the understanding of the kinematic equations of motion, specifically the relationship between height, gravitational acceleration, and final velocity.
Energy Conservation – It also touches on the principle of conservation of energy, where potential energy is converted to kinetic energy as the ball falls.