Estimate the total mechanical work done by the two men in lifting the boat 24 times, assuming they applied the same force to the boat during each lift. (Neglect

Question

The record number of boat lifts, including the boat and its ten crew members, was achieved by Sami Heinonen and Juha Räsänen of Sweden in Estimate the total
mechanical work done by the two men in lifting the boat 24 times, assuming they applied the same force to the boat during each lift. (Neglect any work they may have done allowing the boat to drop back to the ground)2000. They lifted a total mass of 653.2 kg approximately 4 in. off the ground a total of 24 times

Answer 1

In physics, work is simply an amount of force exerted over a distance.  The answer is the two multiplied together (provided you've converted to proper units).

 

To find the force necessary to lift the boat we work with the mass, which is known.  Force is mass time acceleration (F = ma).  We know the mass of the boat, and in this case the acceleration is due to gravity (g = 9.8 m/s^2).  So we get the force (weight) by multiplying the mass and acceleration:  (653.2 kg)x(9.8 m/s^2) = 6401.32 kg m/s^2

 

The weight of the boat (and thus the force required to lift it) is 6401.32 Newtons.

 

Next, we take the force we just determined and use it to find the work to lift the boat once.  As said earlier, work is just force times distance.  It is important to note here that the force is in SI units, while the distance (4 in.) is in English units.  We MUST convert units first.  By definition, 1 inch is equal to 2.54 cm.  Then, 4 inches is equal to 10.16 cm.  100 cm makes 1 meter, so 10.16cm is equal to 0.1016m.

 

Now we're ready to multiply force and distance to get the work:  (6401.32 N)x(0.1016m) = 650.37 Joules

 

The work required to lift the boat once is 650.37 Joules.

 

The last step is to account for lifting it 24 times.  You said that the lowering is neglected (we can assume once its lifted, the boat is dropped).  In this case, it's as easy as just multiplying the work done to lift it once by the 24 times we're going to be lifting it.  (650.37 J)x24 = 15,608.98 J

 

The work required to lift the boat 24 times is 15,608.98 Joules