Question

The answer for part two is below please explain your reasoning for part 1 and 2.

1. In the diagram below, the box is stationary and the angle θ between the horizontal and the applied force is gradually increased (i.e. the force points more downward). Do the following quantities increase, decrease, or remain the same? a) Fx b)左 c) Fv d) fs,.max e) If instead, the box is sliding and θ is increased, does the magnitude of the frictional force on the box increase, decrease, or remain the same? 2. Suppose the block in problem 1 has a mass of 3.5 kg and is pushed along the horizontal floor by a force of magnitude 15 N at an angle θ=40° below the horizontal. The coefficient of kinetic friction between the block and the floor is 0.25. Let the positive direction of the x-axis be to the right. Calculate a) the frictional force on the block from the floor b) the block's acceleration, and c) The work done on the block over 0.5 m of sliding? Suppose the block starts sliding from rest. d) What is the block's velocity after sliding 0.5 m? e) What is the block's velocity after sliding an additional 0.5 m (1.0 m total)? f) What is the instantaneous power on the block as a function of time? g) Verify that integrating the instantaneous power from t 0 s to the time it takes to slide 0.5 m gives the same answer as part c. Answers: a) -11.0N b) 0.140m/s2 c) 0.245 J d) 0.374 m/s e) 0.529 mls f 0.0686 t W

Answer 1

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