That's very interesting. I come up with the same digits as you do, but my
decimal point is in a different place. So, as far as you went, you did a lot
of things right.
Also, notice that the question wants the weight in Newtons, but you've
expressed your answer in kg. That's a mass,not a weight.
Since I can't look over your work, I can't show you where your mistake is.
I guess that means that I have to go all through it . . . I have to show you
mine without ever seeing yours, and when I'm done, I get 5 points. I am
truly psyched for the challenge !
The shaft is a long steel cylinder.
The volume of a cylinder is V = π (radius)² (length)
Diameter = 35 mm = 0.035 meter
Radius = 17.5 mm = 0.0175 meter
Length = 675mm = 0.675 meter
Volume = π (0.0175)² (0.675) cubic meters
(about 0.00065 m³)
Mass = (Volume) x (density) = ( π x (0.0175)² x 0.675 x 7,680 ) kilograms
(about 4.987 kg)
Weight = (mass) x (gravity) = ( π x (0.0175)² x 0.675 x 7,680 ) x (9.81) =
about 48.93 Newtons. (almost exactly 11 pounds)
If you used ' 10 ' for the acceleration of gravity,
then the weight would be about 49.87 Newtons.
If you stopped at mass (kg) then you're off by a factor of 100 .
If you used the mass to find the weight, then you're off by a factor of 10 .
