A 1 kg mass is dropped from a height of 10 m. What is the speed just before it h

Practice Questions

Q1
A 1 kg mass is dropped from a height of 10 m. What is the speed just before it hits the ground?
  1. 5 m/s
  2. 10 m/s
  3. 15 m/s
  4. 20 m/s

Questions & Step-by-Step Solutions

A 1 kg mass is dropped from a height of 10 m. What is the speed just before it hits the ground?
  • Step 1: Identify the mass of the object. In this case, the mass is 1 kg.
  • Step 2: Identify the height from which the object is dropped. Here, the height is 10 m.
  • Step 3: Understand that when the object is dropped, it has potential energy at the height and will convert that energy into kinetic energy just before it hits the ground.
  • Step 4: Write the formula for potential energy (PE) at height: PE = mgh, where m is mass, g is acceleration due to gravity (approximately 9.8 m/s²), and h is height.
  • Step 5: Write the formula for kinetic energy (KE) just before hitting the ground: KE = 0.5mv², where v is the speed just before impact.
  • Step 6: Set the potential energy equal to the kinetic energy: mgh = 0.5mv².
  • Step 7: Since mass (m) is on both sides of the equation, you can cancel it out: gh = 0.5v².
  • Step 8: Rearrange the equation to solve for v²: v² = 2gh.
  • Step 9: Substitute the values for g (9.8 m/s²) and h (10 m) into the equation: v² = 2 * 9.8 * 10.
  • Step 10: Calculate the value: v² = 196.
  • Step 11: Take the square root of both sides to find v: v = sqrt(196).
  • Step 12: Calculate the square root: v = 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.
  • Kinematic Equations – Equations that describe the motion of objects under the influence of forces, particularly in free fall.
  • Gravitational Potential Energy – The energy an object possesses due to its position in a gravitational field, calculated as mgh.
  • Kinetic Energy – The energy of an object in motion, calculated as 0.5mv^2.
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