The best way to prevent back injury is to store materials at level.
a. eye
b. ground
c. waist

For this case, what you must take into account when storing materials is the weight of the materials.

It is convenient that we can store the materials at a level where the back does not have much effort when loading the materials.

At the level of eye, the effort is high because we must move the arms upwards and then carry the weight to the waist.

At ground level the effort is high because we have to tilt our backs to pick up the weight.

The ideal level is the waist because we should not tilt the back, therefore, we make less effort.

The best way to prevent back injury is to store materials at waist level.

option c.

to increase speed you need to decrease frictiona dn drag hense why sprinters wear tight track suits to keep tight against there skin to keep away from wind and decrease the amount of drag you are carrying.a swimmer will wear the tightest swim suit they can possibly fit into (i was a size 28 swim suit at meets i wore a   size 23) why? because the tighter your clothing is the less drag and negative force you have. the heavier the clothe the slower and more wind gets caught. cotton tends to hold onto alot of sweat and water making it slower then say a track suit (no idea what they are made of but they are really comfy around your answer )

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