Does lifting a 90kg person 10m for a minute need 140MJ of energy?
Question asked:
“Lifting a 90 kg person 10 m off the ground and holding them there for one minute with current technology requires about 140 MJ of energy (assuming 35 MJ per litre of fuel).”
Summary
Lifting a 90 kg person 10 m requires roughly 9 kJ of mechanical work (m g h), and holding them stationary adds essentially no additional work. This is orders of magnitude less than 140 MJ, even before accounting for fuel energy density. Therefore the stated energy requirement is vastly overstated.
Sources 60 searched
- OSHA procedures for safe weight limits when manually lifting | Occupational Safety and Health Administration
Other factors include: How often you are lifting something. Whether you bend or twist while lifting. How high an object is lifted. Where the origin of the lift occurs; specifically, whether it is below knuckle height. Whether you hold the object away from you while lifting.
- Lifting Techniques: Why Are We Not Using Evidence To Optimize Movement? - PMC
Lifting something off the ground is an essential task and lifting is a documented risk factor for low back pain (LBP). The standard lifting techniques are stoop (lifting with your back), squat (lifting with your legs), and semi-squat (midway between stoop and squat).
- RECOMMENDED LIMITS FOR ONE-HANDED LIFTING AND LOWERING
RECOMMENDED LIMITS FOR ONE-HANDED LIFTING AND LOWERING · Eric B. Weston, Alex Aurand, Jonathan S. Dufour, Gregory G. Knapik, W. Gary Allread, William S. Marras
- How To Lift A Person Off The Floor — Elearning
They think the "legs" do the work, which is true, but your legs can't do anything if your center of gravity is three feet away from the person you're holding. To help someone up safely, you have to get close. Too close for most people's comfort. You need to be right up against them, bracing your knees against their hips or feet if necessary.
- SAFE LIFTING TECHNIQUES SAFE LIFTING TECHNIQUES
2. Hold the load very close to your body at waist level. 3. Turn the leading foot 90 degrees toward the direction you want to turn.
- Biomechanics of Safe Lifting
If the person is stooped and holding the load in a static posture at the start of the lift, the clockwise moment must equal the counterclockwise moment (or the person would fall over), which means the counterclockwise moment is 1476 in-lbs.
- Work done on lifting/falling things - Solved numerical (video)
In this chapter, we will define the terms 'work' and 'energy'. We will learn how to calculate them, and use them to look at our world in a very different way.
- What is the minimum force required to lift an object? • Physics Forums
The force that lifts his body is the force the scale pushes him up which turned out to be the x N. For a force to lift an object the force must be slightly greater than the object's weight or greater than 600 N . The force which lifted the human ...
- A weight lifter lifts a weight off the ground and holds is up, then
A lift, initially at rest on the ground, starts ascending with constant acceleration 8m//s^(2) After 0.5 seconds, a bolt falls off the floor of the lift. The velocity of the lift at the instant the bolt hits the ground is m/s .[Take g=10 m//s^(2) ]
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