The compressive force per area necessary to break the tibia in the lower leg is about f/a = 1.6 × 108 n/m2 . the smallest cross sectional area of the tibia, about 3.2 cm2 , is slightly above the ankle. suppose a person of mass m = 60 kg jumps to the ground from a height h0 = 2.0 m and absorbs the shock of hitting the ground by bending the knees. assume that there is constant deceleration during the collision with the ground, and that the person lowers their center of mass by an amount d = 1.0 cm from the time they hit the ground until they stop moving.

the simple machine has three main features. they are:

fulcrum is the center point or pivot point of the machine. effort is input force/ applied force. load is external force/ output.

the keisha 's machine labels are

x : load

y: fulcrum

z: lever

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.

not too sure thinking all accelerations are pointed down