A grasshopper jumps by extending its back legs from a folded postion, so that they thrust against the ground.
To get a good jump requires two things.
[Science stuff: equations of motion and some facts and figures]
Note: these cartoons are only for illustration - they are not tracings from real jumping grasshoppers.
So remember, a good jump means that the legs must push against the ground with high force, and high speed.
To be precise (or reasonably so), a typical grasshopper weighing 2-3 gm will thrust against the ground with a force which peaks at about 30 gms when the legs are half extended, to give it a final take-off velocity of about 3 m.s-1.
[For future reference: note how in the good jump there is a slight delay between the initial crouch and the actual jump. This delay is crucial, as we shall see later.]
The ultimate source of this push comes from the contraction of the muscles inside the leg, so let's start off by seeing how the muscles make the leg move...