A 4 kg object is moving with a speed of 5 m/s. What is the total mechanical ener

Practice Questions

Q1
A 4 kg object is moving with a speed of 5 m/s. What is the total mechanical energy if it is at a height of 2 m?
  1. 50 J
  2. 60 J
  3. 70 J
  4. 80 J

Questions & Step-by-Step Solutions

A 4 kg object is moving with a speed of 5 m/s. What is the total mechanical energy if it is at a height of 2 m?
  • Step 1: Identify the mass of the object, which is 4 kg.
  • Step 2: Identify the speed of the object, which is 5 m/s.
  • Step 3: Identify the height of the object, which is 2 m.
  • Step 4: Calculate the kinetic energy using the formula: Kinetic Energy = 0.5 × mass × (speed)².
  • Step 5: Substitute the values into the kinetic energy formula: Kinetic Energy = 0.5 × 4 kg × (5 m/s)².
  • Step 6: Calculate (5 m/s)², which is 25 m²/s².
  • Step 7: Multiply: 0.5 × 4 kg × 25 m²/s² = 50 J. This is the kinetic energy.
  • Step 8: Calculate the potential energy using the formula: Potential Energy = mass × gravity × height.
  • Step 9: Use the value of gravity as approximately 9.8 m/s².
  • Step 10: Substitute the values into the potential energy formula: Potential Energy = 4 kg × 9.8 m/s² × 2 m.
  • Step 11: Multiply: 4 kg × 9.8 m/s² = 39.2 kg·m/s² (which is the same as 39.2 N).
  • Step 12: Now multiply by height: 39.2 N × 2 m = 78.4 J. This is the potential energy.
  • Step 13: Add the kinetic energy and potential energy to find the total mechanical energy: Total Mechanical Energy = Kinetic Energy + Potential Energy.
  • Step 14: Substitute the values: Total Mechanical Energy = 50 J + 78.4 J.
  • Step 15: Calculate the total: 50 J + 78.4 J = 128.4 J.
  • Kinetic Energy – The energy an object possesses due to its motion, calculated as 0.5 × mass × velocity².
  • Potential Energy – The energy an object possesses due to its position in a gravitational field, calculated as mass × gravitational acceleration × height.
  • Total Mechanical Energy – The sum of kinetic and potential energy in a system.
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