A force of 6 N acts horizontally on a stationary mass of 2 kg for 4 s. The kinetic energy in Joule is:
Correct answer: B. 144
- A. 12
- B. 144
- C. 72
- D. 48
Explanation
To determine the kinetic energy of the mass after 4 seconds, apply Newton's second law. Given that the force (F) is 6 N and the mass (m) is 2 kg, we first find the acceleration (a) using F = ma, resulting in a = 3 m/s².Initially, the object is stationary, so the initial velocity (u) is 0. The final velocity (v) can be calculated using v = u + at, where t is 4 seconds, giving v = 12 m/s.Now, calculate the kinetic energy (KE) using the formula KE = 1/2 mv². Substituting the values, KE = 1/2 × 2 × (12)² = 144 J.The other options are incorrect due to either a miscalculation of velocity or an incorrect application of the kinetic energy formula.
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Kinetic energy is the energy of motion, given for a nonrelativistic object by K = ½mv², so it depends on mass and the square of speed. Questions connect kinetic energy with work through the work energy theorem, calculate changes in kinetic energy, and distinguish it from momentum and potential energy.
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