A ball is thrown vertically upwards with a speed of 30 m/s. What is the maximum

Practice Questions

Q1
A ball is thrown vertically upwards with a speed of 30 m/s. What is the maximum height it reaches? (g = 9.8 m/s²)
  1. 45.9 m
  2. 46.0 m
  3. 46.1 m
  4. 46.2 m

Questions & Step-by-Step Solutions

A ball is thrown vertically upwards with a speed of 30 m/s. What is the maximum height it reaches? (g = 9.8 m/s²)
Correct Answer: 45.9 m
  • Step 1: Understand that when the ball is thrown upwards, it has initial speed and will rise until it stops momentarily at the maximum height.
  • Step 2: Recognize that at the maximum height, all the initial kinetic energy (energy of motion) will be converted into potential energy (stored energy due to height).
  • Step 3: Write down the formula for kinetic energy: KE = 0.5 * m * v², where m is mass and v is initial speed (30 m/s).
  • Step 4: Write down the formula for potential energy at maximum height: PE = m * g * h, where g is the acceleration due to gravity (9.8 m/s²) and h is the height we want to find.
  • Step 5: Set the initial kinetic energy equal to the potential energy at maximum height: 0.5 * m * v² = m * g * h.
  • Step 6: Notice that the mass (m) cancels out from both sides of the equation, simplifying it to: 0.5 * v² = g * h.
  • Step 7: Rearrange the equation to solve for height (h): h = v² / (2 * g).
  • Step 8: Substitute the values into the equation: h = (30)² / (2 * 9.8).
  • Step 9: Calculate (30)² = 900, and then calculate 2 * 9.8 = 19.6.
  • Step 10: Divide 900 by 19.6 to find h: h = 900 / 19.6 ≈ 45.9 m.
  • Kinematics – The study of motion, specifically how objects move under the influence of forces.
  • Conservation of Energy – The principle that energy cannot be created or destroyed, only transformed from one form to another.
  • Gravitational Potential Energy – The energy an object possesses due to its position in a gravitational field, calculated as mgh.
  • Kinetic Energy – The energy an object has due to its motion, calculated as 0.5mv².
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