Question:
A boy of mass 50 kg runs with a speed of 4 m/s. His kinetic energy is-
A boy of mass 50 kg runs with a speed of 4 m/s. His kinetic energy is-
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Kinetic energy depends on the square of velocity. If velocity doubles, kinetic energy becomes four times.
Updated On: Jun 9, 2026
- 40 J
- 4 J
- 400 J
- 0.4 J
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The Correct Option is C
Solution and Explanation
Concept:
The kinetic energy of a moving body is given by
\[
KE=\frac12 mv^2
\]
where \(m\) is mass and \(v\) is velocity.
Step 1: Write the given data.
Mass of the boy, \[ m=50\text{ kg} \] Speed of the boy, \[ v=4\text{ m/s} \]
Step 2: Substitute in the kinetic energy formula.
\[ KE = \frac12 \times 50 \times (4)^2 \] \[ = 25\times16 \] \[ =400\text{ J} \]
Step 3: State the answer.
Therefore, \[ \boxed{KE=400\text{ J}} \] 400 J
Step 1: Write the given data.
Mass of the boy, \[ m=50\text{ kg} \] Speed of the boy, \[ v=4\text{ m/s} \]
Step 2: Substitute in the kinetic energy formula.
\[ KE = \frac12 \times 50 \times (4)^2 \] \[ = 25\times16 \] \[ =400\text{ J} \]
Step 3: State the answer.
Therefore, \[ \boxed{KE=400\text{ J}} \] 400 J
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