Work-energy Theorem

Mediumphysics

Net work on a 4 kg body is 80 J from rest. Final speed?

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4.47 m/s

6.32 m/s

8.94 m/s

12.6 m/s

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Subject: physics
Chapter: work, energy and power
Topic: work-energy theorem
Difficulty: Medium
Year: 2025

Solution

Correct Answer:

6.32 m/s

Work-Energy Theorem: The net work done on an object is equal to its change in kinetic energy ( $W_{n e t} = Δ K$ ).
Constraint: Since it starts from rest, $K_{ini t ia l} = 0$ .
Formula: $W_{n e t} = \frac{1}{2} m v^{2}$ .
Solve for v:
- $v^{2} = \frac{2 W}{m}$
- $v = \frac{2 \times 80}{4} = \frac{160}{4} = 40$ .
Calculation: $40 \approx 6.3245$ m/s.
Result: Final speed is $6.32$ m/s.

This medium difficulty physics question is from the chapter work, energy and power, covering the topic of work-energy theorem. It appeared in the 2025 exam.

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Work-energy Theorem

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