A 2.0 kg box is pulled along a horizontal frictionless surface by a rope that makes an angle of 30° above the horizontal. The tension in the rope is 10 N. What is the acceleration of the box? (Use cos 30° = 0.87 and sin 30° = 0.50.)
Show the answer and explanation
Correct answer
B. 4.3 m/s²
Principle or equation
Newton's second law: the net force in the horizontal direction equals mass times acceleration. Only the horizontal component of the tension contributes to horizontal acceleration.
Why this answer is correct
The horizontal component of the tension is T cos 30° = 10 × 0.87 = 8.7 N. Since the surface is frictionless, the net horizontal force is 8.7 N. Using F = ma, a = 8.7 / 2.0 = 4.35 m/s², which rounds to 4.3 m/s².
Example
If the same tension were applied horizontally (angle 0°), the acceleration would be 10/2 = 5 m/s².
This published item includes a stored explanation and passed the platform’s publication workflow. It is independent preparation material, not a claim of an official or recalled examination question.