A stone S is sliding on ice. The stone is moving along a straight line ABC, where AB = 24 m and AC = 30 m. The stone is subject to a constant resistance to motion of magnitude 0.3 N. At A the speed of S is 20 m s–1, and at B the speed of S is 16 m s–1. Calculate
(a) the deceleration of S,
(b) the speed of S at C.
(c) Show that the mass of S is 0.1 kg.
At C, the stone S hits a vertical wall, rebounds from the wall and then slides back along the line CA. The magnitude of the impulse of the wall on S is 2.4 N s and the stone continues to move against a constant resistance of 0.3 N.
(d) Calculate the time between the instant that S rebounds from the wall and the instant that S comes to rest.
a.) a=-3m/s², Deceleration of S is 3m/s²
b.) v=14.83m/s
c.) Proven m=0.1kg
d.) I have worked it out both ways, however - Do you have to take <-- as the positive direction because the Impulse is 2.4? Or can you work it the other way round by taking I=-2.4 and --> as the positive direction?