Question: The model airplane in the figure below has a mass of 0.80 kg and moves at a constant speed on a circle that is parallel to the ground. Assume that there is no upward lift on the plane generated by its wings. Without such lift, the guideline slopes downward due to the weight of the plane. Find the tension T in the guideline (length = 18 m), for purposes of significant figures, use 0.800 kg for the mass of the plane, 18.0 m for the length of the guideline, and s1 = 18.0 and s2 = 41.0 m/s for the speeds. This is a practice question and the answers are given.
Tension for s1: 17.8 N
Tension for s2: 75.5 N

Please tell me the equation/method used to achieve these answers.

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.