Question detail
A car has a kinetic energy of 120 000 J and is moving at 20 m s⁻¹. What is the mass of the car in kilograms?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Energy changes in a system, and the ways energy is stored before and after such changes
Question
- A. 120 000
- B. 20
- C. 2 400
- D. 6 000
Answer
2 400
Explanation
Using Ek = 0.5 m v², rearrange to m = 2Ek/v². Substituting gives 2×120 000/(20²)=2 400 kg.
Common mistake
Confusing Units of Measurement
Students often confuse kinetic energy measured in joules with mass measured in kilograms and speed measured in metres per second.
Always remember that kinetic energy is expressed in joules (J), mass in kilograms (kg), and speed in metres per second (m/s). Keep the units distinct and practice converting between them if necessary.
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