A tennis ball launcher works by using a spring to propel the ball forward.
One model of tennis ball launcher has
advertised that it is capable of imparting
15,000 J of kinetic energy to a 0.5 kg ball
initially at rest. A student carefully measures the
compression of the spring to be 0.10 m.
What is the value of the spring constant for the
tennis ball launcher according to the data
provided?

Which of the following are considered noble gases? a. bromine b. neon c. argon d. chlorine

The ultracentrifuge is an important tool for separating and analyzing proteins. because of the enormous centripetal accelerations, the centrifuge must be carefully balanced, with each sample matched by a sample of identical mass on the opposite side. any difference in the masses of opposing samples creates a net force on the shaft of the rotor, potentially leading to a catastrophic failure of the apparatus. suppose a scientist makes a slight error in sample preparation and one sample has a mass 10 mg larger than the opposing sample. if the samples are 12 cm from the axis of the rotor and the ultracentrifuge spins at 70,000 rpm, what is the magnitude of the net force on the rotor due to the unbalanced samples? ( be thorough on your answer)

Air is contained in a variable-load piston-cylinder device equipped with a paddle wheel. initially, air is at 400 kpa and 17°c. the paddle wheel is now turned by an external electric motor until 75 kj/kg of work has been transferred to air. during this process, heat is transferred to maintain a constant air temperature while allowing the gas volume to triple. calculate the required amount of heat transfer in kj/kg.