A plank, fixed to a sled at rest in frame S, is of length Lo and makes an angle of θ0 with...

A plank, fixed to a sled at rest in frame S, is of length Lo and makes an angle of θ0 with the x-axis. Later, the sled zooms through frame S at a constant speed v parallel to the x-axis. Show that according to an observer who remains at rest in frame S, the length of the plank is now

and the angle it makes with the x-axis is