Learning Goal: To practice Problem-Soving Strategy 6.1 for Newtonian mechanics p

Question

Learning Goal: To practice Problem-Soving Strategy 6.1 for Newtonian mechanics problems. A box of mass 3.1 kg slides down a rough vertical wall. The gravitational force on the box is 30 N. When the box reaches a speed of 2.5 m/s, you start pushing on one edge of the box at a 45° angle (use degrees in your calculations throughout this problem) with a constant force of magnitude Fp 23 N. as shown in (Figure 1). There is now a frictional force between the box and the wall of magnitude 13 N. How fast is the box sliding 2.2s after you started pushing on it? Figure 1 of 1> 45°

Explanation / Answer

speed = 2.5m/sec

UP component of applied force = (sin 45 * 23) = 16.263N.

frictional force = 13 N

Total force acting upwards = (16.263 + 13) = 29.263N.

The weight of the box is (3.1 * g) = 30.38N.

Net accelerating force now operating = (30.38 - 29.263) = 1.117 N.

The acceleration is still positive.

Acceleration = (f/m) = 1.117/3.1 = 0.36 m/sec^2.

After 2.2 second the box has gained (at) = 0.36 x 2.2) = 0.792 m/sec.

Final speed after 2.2 second = (2.5 + 0.792) = 3.292 m/sec

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