A helicopter lifts a 72 kg astronaut 15 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/10. How much work is done on the astronaut by (a) the force from the helicopter and (b) the gravitational force on her? Just before she reaches the helicopter, what are her (c) kinetic energy and (d) speed?

a)

b)

c)

d)

Explanation:

Given:

a)

Now the force of lift by the helicopter:

Here the lift force is the resultant of the force of gravity being overcome by the force of helicopter.

where:

b)

The gravitational force on the astronaut:

d)

Since the astronaut has been picked from an ocean we assume her initial velocity to be zero,

using equation of motion:

c)

Hence the kinetic energy:

578.66 N

Explanation:

The first step is to calculate the mass

mgh= 3200J

3200/9.8×5.53

3200/54.194

m = 59.047 kg

Therefore the weight can be calculated as follows

Weight = m × g

= 59.047 × 9.8

= 578.66 N