Question

1. A black engine is being pulled by a 3[N] force (green arrow). The mass of the engine is 2 [kg]. The mass of the red car behind it is 1 [kg]. Assume that they are moving on a level surface with coefficient of kinetic friction of m_k=0.2. What is the force by the red car on the black engine? and draw free body diagram

Answer 1

Im = 2kg Black engine. F Red car T mass of xan black engine. IN fears Imt mor m₂ = 1kg Smass of red car. IF = 34 >Applied force on engene. T is force between the engine and can Taking car and engine as a systein: Along vertical; f N = (m. Mr) g (M + Mr)g -> N=12+1)x9.8N Na 29.4n Met normal force Maseinum static friction available = N = 0.2% 29.4N man = 5-839 But applied force is 3N only. So system will not move. mas 'S max

IN Along vertical: ott mg on engine. » In mare For engine only >F No= mbg » Ny=2x9.8N N=19.6N / Normal ... Masimum frection available for engine is formas= No = 0.2 x 19.6N = 3.92 Sence, masimum available static fradron is greater than required force to stop the motion, so magnitude of static frection on the engine will be Ifo=f=30 So, there is no need of I, to stop the motion of engene. Hence, force by the red car on black engine is zero.