A 2 kg object is dropped from a height of 10 m. What is the speed of the object

Practice Questions

Q1
A 2 kg object is dropped from a height of 10 m. What is the speed of the object just before it hits the ground? (g = 9.8 m/s²)
  1. 10 m/s
  2. 14 m/s
  3. 20 m/s
  4. 30 m/s

Questions & Step-by-Step Solutions

A 2 kg object is dropped from a height of 10 m. What is the speed of the object just before it hits the ground? (g = 9.8 m/s²)
  • Step 1: Identify the mass of the object (m = 2 kg) and the height from which it is dropped (h = 10 m).
  • Step 2: Use the acceleration due to gravity (g = 9.8 m/s²).
  • Step 3: Understand that when the object is dropped, its potential energy at the height will convert to kinetic energy just before it hits the ground.
  • Step 4: Write the equation for potential energy (PE = mgh) and kinetic energy (KE = 0.5mv²).
  • Step 5: Set the potential energy equal to the kinetic energy: mgh = 0.5mv².
  • Step 6: Notice that the mass (m) cancels out from both sides of the equation.
  • Step 7: Rearrange the equation to solve for v (the speed just before hitting the ground): v² = 2gh.
  • Step 8: Substitute the values of g and h into the equation: v² = 2 × 9.8 m/s² × 10 m.
  • Step 9: Calculate the right side: v² = 196 m²/s².
  • Step 10: Take the square root of both sides to find v: v = sqrt(196 m²/s²) = 14 m/s.
  • Energy Conservation – The principle that the total mechanical energy (potential + kinetic) in a closed system remains constant if only conservative forces are acting.
  • Kinematics – The study of motion without considering the forces that cause it, particularly the equations relating distance, speed, and acceleration.
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