Calculating work done by helicopter/gravity, kinetic energy and speed?

In summary: No, the pilot is burning fuel to keep the rope taut, but the pilot is not lifting the astronaut vertically, so the force exerted by the rope is not equal to her weight.F=maF=(90)(9.8/12)=73.5W=(73.5)(13)=955.5The work done on the astronaut is 955.5 Joules by the helicopter and -955.5 Joules by gravity.In summary, the helicopter exerts a force of 73.5 N on the astronaut, and does 955.5 Joules of work on her. The gravitational force on her is also 73.5 N, and does -955.5 Joules of
  • #1
rockchalk1312
38
0
A helicopter lifts a 90 kg astronaut 13 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/12. 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?


F=ma
W=Fd
KE=1/2mv2


F=ma
F=(90)(9.8/12)=73.5
W=(73.5)(13)=955.5

Was not the right answer for a...for b I tried using Wg=-mgd but that didn't seem to work either. Am I misinterpreting what g/12 means? a and b were as far as I got. :( Any help would be appreciated, thank you!
 
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  • #2


rockchalk1312 said:
A helicopter lifts a 90 kg astronaut 13 m vertically from the ocean by means of a cable. The acceleration of the astronaut is g/12. 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?


F=ma
There are two forces acting on her. Consider - if the astronaut were just dangling there without moving, is the force exerted by the rope = ma = 0?
 

1. How is work done by a helicopter or gravity calculated?

The work done by a helicopter or gravity is calculated by multiplying the force applied by the distance over which the force is applied. This can be expressed as W = F x d, where W is work, F is force, and d is distance.

2. What is the formula for calculating kinetic energy?

The formula for calculating kinetic energy is KE = 1/2 x m x v^2, where KE is kinetic energy, m is the mass of the object, and v is the velocity of the object.

3. Can kinetic energy and speed be calculated from the work done by a helicopter?

Yes, they can. The work done by a helicopter can be used to determine the change in kinetic energy of an object, which can then be used to calculate the object's speed using the formula v = √(2 x KE/m).

4. How does the work done by gravity affect an object's kinetic energy?

The work done by gravity can either increase or decrease an object's kinetic energy, depending on the direction in which the force is applied. If the force is applied in the same direction as the object's motion, it will increase the kinetic energy. If the force is applied in the opposite direction, it will decrease the kinetic energy.

5. Is the work done by a helicopter or gravity dependent on the object's mass?

No, the work done by a helicopter or gravity is not dependent on the object's mass. The amount of work done is determined by the force applied and the distance over which the force is applied, not the mass of the object. However, the resulting change in kinetic energy and speed may vary depending on the mass of the object.

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