Kristen decides to go sledding with her sister Mary after a huge snowstorm. Kristen has a mass of 50kg and Mary has a mass of 57.5kg.
Both sisters take turns, pushing each other down the large hill. The free
diagram shows the forces acting on the sled. If the sled has a mass of
5kg, and each sister rides the sled with the same forces, what is the rate
of acceleration for both Kristin and Mary?

An object of dimensions 50 cm x 40 cm x 0.20 cm has a mass 60g. find its density in g/cm3 and kg/ m3

Air enters a gas turbine with two stages of compression and two stages of expansion at 100 kpa and 17°c. this system uses a regenerator as well as reheating and intercooling – the intercooler returns the air to the inlet temperature. the pressure ratio across each compressor is 4 ; 300 kj/kg of heat are added to the air in each combustion chamber; and the regenerator operates perfectly while increasing the temperature of the cold air by 20°c. determine the system’s thermal efficiency. assume isentropic operations for all compressor and the turbine stages and use constant specific heats at room temperature. (0.378)

Suppose that three astronomical objects, 1, 2, and 3 are observed to lie on a line, and the distance from object 1 to object 3 is d. object 1 has four times the mass of object 3, and seven times the mass of object 2. find the distance between objects 1 and 2 for which the net force on object 2 is zero.