9. Carlos jumps out of a hovering helicopter. After he opens his parachute, his acceleration due to gravity decreases to zero. This is because

A The force of air resistance becomes equal in magnitude to his weight.

B. The force of gravity has become zero.

C. Air resistance must be zero

D. He must have struck the ground,

A The force of air resistance becomes equal in magnitude to his weight.

Explanation:

When Carlos jumped out of the helicopter, he fell with a downward force which is proportional to his weight.

His weight is the product of his mass and acceleration due to gravity.

When the parachute is deployed, air resistance between the air molecules and the surface area of the parachute generates a drag force, which acts upwards.

If the drag forces exceeds his weight, then his net force will be directed upwards.

If his weight exceeds the drag forces, then the net force on his body will be downwards.

In the case that his drag force, and his weight are equal, there will be a zero net force on him, and he will experience no acceleration.

So, if after he opens his parachute, his acceleration due to gravity decreases  to zero, then we can say that this is because  the force of air resistance (drag) becomes equal in magnitude to his weight.

the answer is d. 4

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