Question

An object A moving horizontally with kinetic energy of 800 J experiences a constant opposing force of 100 N, while moving from a place x to a place y, where xy is 2 m. What is the energy of A at y?

• A. 700 J
• B. 400 J
• C. 600 J
• D. 300 J

Hint:

Opposing forces reduce kinetic energy. Always use negative work for resistive forces.

Answer 1

The Correct Option is C

Concept: Work-energy theorem: \[ W = \Delta K = K_f - K_i \] Work done by opposing force is negative: \[ W = -F \cdot s \]

Step 1: Work done by force.
\[ W = -100 \times 2 = -200 \, \text{J} \]

Step 2: Final kinetic energy.
\[ K_f = K_i + W = 800 - 200 = 600 \, \text{J} \]