# Help! Hiker stucked!

A $$80 \text{kg}$$ hiker is trapped on a mountain ledge following a storm calling for help.

Then, a helicopter rescues the hiker by hovering above him and lowering a cable to him. The mass of cable is $$8\text{kg}$$, and its length is $$15 \text{m}$$. A sling of mass $$70 \text{kg}$$ is attached to the end of the cable. The hiker attaches himself to the sling, and the helicopter then accelerates upward.

Terrified by hanging from the cable in mid-air, the hiker tried to signal the pilot by sending transverse pulses up the cable. It takes the pulse of $$0.25$$ seconds to travel the length of the cable.

what is the acceleration of the helicopter?

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