Give reasons for the following :

a] A helicopter must have two sets of blades in order to fly with stability.

b) If you are in an elevator and the cable breaks, jumping out just before the elevator hits the ground would not save you.

c)You usually jerk a paper towel from a roll in order to tear it instead of pulling it smoothly.

d) The stronger, heavier team in a tug of war does not create a larger tension in the rope than the weaker, lighter team.

b)

When the cable of an elevator breaks, it begins to fall freely under gravity. With the elevator the person inside is also falling freely and gaining velocity. Just before hitting the ground the velocity attained by the person may be so much that it is enough to kill the person when he hits the ground.

d)

The tension developed in the rope in a tug-of-war game is due to the force by both weak and strong team. If any one team leaves the rope, then there will be nearly zero tension on the rope.

For help with more answers you may post them individually.