Basic Requirements

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.

• First, the legs have to thrust on the ground with a lot of force.
  If the thrust is too low, the animal doesn't get a fast enough take-off and it doesn't jump very far.
• Second, the legs have to develop this force quickly.
  If the thrust builds up too slowly, the legs will extend before the thrust reaches its maximum. Once the grasshopper is standing on tip-toe, it can't thrust against the ground any more.

[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...