Calculate focal length of a magnifying lens that produces a virtual image at a distance of 26 mm when the object is placed 15 mm away

After a big snowfall, you take your favorite rocket-powered sled out to a wide field. the field is 195 m across, and you know that your sled accelerates at a rate of 3.65 m/s2 when the rocket is on. how much time will it take the sled to cross the field starting from rest, assuming the rocket is on the whole time?

If 2 moles of co_2 at 2l and 500k are expanded reversibly to 20l, more work can be obtained from an adiabatic process than from an isothermal process. is the above statement true or false?

Arope has one end tied to a vertical support. you hold the other end so that the rope is horizontal. if you move the end of the rope back and forth with a frequency of 4 hz, the transverse wave you produce has a wavelength of 0.5 m. what is the speed of the wave in the rope?