When a person bends an arm a different muscle is used to bring it back to the original position. why can't the same muscle be used to both bend and unbend the arm?

Nitrogen (n2) undergoes an internally reversible process from 6 bar, 247°c during which pν1.2 = constant. the initial volume is 0.1 m3 and the work for the process is 121.14 kj. assuming ideal gas behavior, and neglecting kinetic and potential energy effects, determine heat transfer, in kj, and the entropy change, in kj/s. show the process on a t-s diagram.

Aparticle moves in a circle 1.50 m in radius . through what angle in radians does it rotate if it moves through an arc length of 2.50m? what is the angle in degrees?

At what time would the velocity reach 60.00 km/hr? it will never travel at 60.00 km/hr. it travels at a different constant rate. 10.00 seconds 100.00 seconds