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Question · Revise, Reflect, Refine, Q14, page 113
An object of mass 2 kg moving with a constant velocity of 10 m s⁻¹ encounters a rough patch where the force of friction on the object is 7 N. At the same time, an additional constant force of 3 N opposing the motion is applied on the object. After entering the rough patch, how much distance does the object travel before coming to rest?
![Question 14 — An object of mass - How Forces Affect Moti - [Teachoo] - Questions at the end of the chapter](https://cdn.teachoo.com/ac1f12ae-7313-47f1-9793-5ade696d92d2/animation-for-an-object-of-mass-2-kg-moving-with-a-constant-velocity-of-10-m-s-encounters-a-rough-patch-where-the-for.gif)
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Answer
- Given: m = 2 kg, u = 10 m s⁻¹, v = 0 m s⁻¹
- Both forces oppose the motion, so they act in the same direction and add up.
- Net force = 7 N + 3 N = 10 N, opposite to the motion
- Acceleration, a = F / m = −10 / 2 = −5 m s⁻²
- Using v² = u² + 2as, 0 = (10)² + 2 × (−5) × s
- s = 10 m
- Answer: The object travels 10 m before coming to rest.
