Question

Force vectors (a) (10 points) Here a stone is suspended at rest by a string. The weight is drawn as a (white) vector arrow. Draw a vector for the missing force acting on the stone. As the origin of the vector, choose the same point from which the weight is drawn. Hint: ask what the net force on the stone must be. NOTE: the rules for where to draw force arrows are very flexible. Think of arrows as thrusters, and then attach arrows wherever the thrusters would have the same effect as the real (external) forces acting on the object of the problem. (b) (10 points) Here a stone is being accelerated vertically upward with acceleration a 9.8m/s2. Dravw a vector for the missing force acting on the stone. As the origin of the vector, choose the same point from which the weight is drawn. Hint: you don't need to know the mass of the stone because the lengths of force arrows are always relative. Ask how large the missing force must be in relation to the weight (weight = m × g).

Answer 1

(a)In this case, the net force on the stone is zero, that's is why its hanging without any hindrance.

The missing force is the tension in the string, acting in apposite direction as shown in the picture uploaded. The length of the arrow shows that the downward force(weight) and the upward force(tension) are same in magnitude.

(b)In this case, when the stone is moving upwards, clearly there is no balance.

The missing force is still the tension but this time its of course greater than the weight.

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