Atrain consists of a 60 mg engine and three cars, each having a mass of 30 mg . if it takes 75 s for the train to increase its speed uniformly to 42 km/h, starting from rest, determine the force t, developed at the coupling between the engine e and the first car a. the wheels of the engine provide a resultant frictional tractive force f which gives the train forward motion, whereas the car wheels roll freely.

Ablock of mass m = 2.5 kg is attached to a spring with spring constant k = 740 n/m. it is initially at rest on an inclined plane that is at an angle of theta= 26 with respect to the horizontal, and the coefficient of kinetic friction between the block and the plane is uk = 0.17. in the initial position, where the spring is compressed by a distance of d = 0.16 m, the mass is at its lowest position and the spring is compressed the maximum amount. take the initial gravitational energy of the block as zero. the block's initial mechanical energy is 9.472 j.b. if the spring pushes the block up the incline, what distance l in meters will the block travel before coming to rest? the spring remains attached to both the block and the fixed wall throughout its motion.