Question

Johnny and Wendy were walking down the street when they saw a mysterious man frozen in ice, just like the one below. Johnny said the man should be brought to the police station and started to push the man to the east with 50 N. Wendy, on the other hand, said the man should be taken to a hospital and started pushing the man to the west with 40 N. Given that the man was inside the block of ice, assume there was no frictional force between the man and ice and the ground. The mass of the man and the ice was 75 kg. 8.

Answer 1

(a) The FBD is shown in fig Net force and acceleration of the man + black will be towards East. (b) Net force on the man in ice, F_net = (50 - 40) = 10N Mass of man in ice, m = 75 kg therefore Acceleration of man in ice, a = F_net/m = (10/75)m/s^2 = 0.14 m/s^2 (c) Using, s = ut + 1/2 at^2, where, t = 3 sec, u = 0 (initially blackman is at rest) a = 0.14 m/s^2, we have, Distance travelled by the box, s = 0 times 3 + 1/2 times 0.14 times 3^2 = 0 + 0.07 times 9 = 0.63m (d) Let, v be the final velocity, then a = v - u/t, where, t = 3 sec, a = 0.14 m/s^2, we have, 0.14 = v - 0/3 therefore Final velocity, v = (3 times 0.14) = 0.42 m/s \r\n (e) Kinetic energy, k = 1/2 mv^2 = [1/2 times 75 times (0.42)^2]