Question

physics homework

3. Three masses 10 kg, 30 kg and 20 kg are connected by two massless strings. 30 Kg mass is on top of a table and the other two masses pass over two different pulleys and hang down. The 20 kg mass has an acceleration of 0.2 m/s. What is the coefficient of kinetic friction between the table and 30 kg mass? A rectangular wooden plank of length 2m and width 1 m is fastened to 4 legs at the four corners of the plank and is standing like a dining table. The wooden plank has a mass of 10 kg ang the mass of each leg is 1 kg. The length of each leg is 2 m. where is the center of mass located? A ramp is elevated at an angle of 45. A 10 kg mass is pulled up on the ramp, by a rope at an acceleration of 1 m/s'. The coefficient of kinetic friction is 0.5. What is the tension in the rope? A 100 g object was located at (1, 1) m. A force F (2i+2)) N acts on it.Calculate the torque about the origin. If the velocity of the object at that instant is v (i+j) m/s, what was the angular momentum? 4. 5. 6.

Answer 1

tau = r vector times F vector = (1i^^+ 1j^^) times (2i^^+ 2j^^) = 2k^^- 2k^^Torque = 0 angular momentum l = r vector times mv vector = (i^^+ 1j^^) times (i^^+ j^^) times 100 (k^^- k^^) times 100 = 0 N = 10 g cos 45 = 69.36 N f_k = mu_0 N = 34.68 N T - f_k = 10 a T = 10 times 1 + 34.68 = 44.68 N -f_k + T_2 - T_1 = 30 times 0.2 = 6 T_1 - 10g = 10 a T_1 = 2 + 10 g 20g - T_2 = 20 a T_2 = 20g + 4 f_k = mu_k times 30 g -mu_k 30g + 20g + 4 - 2 10g = 6 mu_k 30 g = 10 g + 2 - 6 = 94.1 mu_k = 0.319