A block of mass 2 kg is released from a height of 10 m. What is its speed just b

Practice Questions

Q1
A block of mass 2 kg is released from a height of 10 m. What is its speed just before it hits the ground? (g = 9.8 m/s²)
  1. 14 m/s
  2. 20 m/s
  3. 10 m/s
  4. 5 m/s

Questions & Step-by-Step Solutions

A block of mass 2 kg is released from a height of 10 m. What is its speed just before it hits the ground? (g = 9.8 m/s²)
  • Step 1: Identify the mass of the block, which is 2 kg.
  • Step 2: Identify the height from which the block is released, which is 10 m.
  • Step 3: Identify the acceleration due to gravity, which is 9.8 m/s².
  • Step 4: Use the formula for potential energy (PE) at height: PE = mgh, where m is mass, g is gravity, and h is height.
  • Step 5: Calculate the potential energy: PE = 2 kg * 9.8 m/s² * 10 m = 196 Joules.
  • Step 6: Use the formula for kinetic energy (KE) just before hitting the ground: KE = 0.5 * m * v², where v is the speed.
  • Step 7: Set the potential energy equal to the kinetic energy: 196 Joules = 0.5 * 2 kg * v².
  • Step 8: Simplify the equation: 196 = 1 * v², so v² = 196.
  • Step 9: Take the square root of both sides to find v: v = sqrt(196) = 14 m/s.
  • Conservation of Energy – The principle that energy cannot be created or destroyed, only transformed from one form to another, in this case from potential energy to kinetic energy.
  • Kinetic and Potential Energy – Understanding the relationship between potential energy (mgh) and kinetic energy (0.5mv²) in the context of an object in free fall.
  • Free Fall Motion – The motion of an object under the influence of gravity alone, without any other forces acting on it.
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