Calculating the work against gravity?

  • Thread starter Thread starter mscott
  • Start date Start date
  • Tags Tags
    Gravity Work
AI Thread Summary
To calculate the work against gravity for building a brick tower with a height of 20 feet and a base of 10 feet, the volume of each layer is determined to be 100Δy ft³. The mass of each layer is calculated using the brick's density of 80 lb/ft³, resulting in a force of 78,400 lb acting on each layer. The integral of this force over the height of the tower is computed, but there is a discrepancy with the expected answer in the solutions manual, which states the work should be 1.6x10^6 ft-lb. The correct acceleration due to gravity is clarified as 32 ft/s², which is essential for accurate calculations. This discussion highlights the importance of using the correct gravitational constant in work calculations against gravity.
mscott
Messages
4
Reaction score
0
Calculate the work against gravity require to build the structure out of brick. Assume the brick has a density of 80 lb/ft^3.

A tower has a height of 20ft and a square base of side 10ft.

This is what I tired to do. I may have gotten it right, but the units or something may have been off. I am hoping one of you will be able to help me.

Volume of layer = 10 x 10 Δy ft^3 = 100Δy ft^3
Mass of layer = 80 lb/ft^3 x 100Δy ft^3
Force on layer = 9.8 x 80 x 100Δy = 78400

Taking the integral of 78400y from limits 0 to 20 equals 15,680,000, but the answer in my solutions manual says the answer should be 1.6x10^6 ft-lb.

Can anyone help me out?
 
Physics news on Phys.org
What is the acceleration of gravity in ft/s2?
 
I'm not sure. Those were the only givens.
 
I guess you are supposed to know that g = 32 ft/s2. Use that.
 

Thread 'Errors and significant figures'

I multiplied the values first without the error limit. Got 19.38. rounded it off to 2 significant figures since the given data has 2 significant figures. So = 19. For error I used the above formula. It comes out about 1.48. Now my question is. Should I write the answer as 19±1.5 (rounding 1.48 to 2 significant figures) OR should I write it as 19±1. So in short, should the error have same number of significant figures as the mean value or should it have the same number of decimal places as...
View full post »
Thread 'Collision of a bullet on a rod-string system: query'

Thread 'Collision of a bullet on a rod-string system: query'

In this question, I have a question. I am NOT trying to solve it, but it is just a conceptual question. Consider the point on the rod, which connects the string and the rod. My question: just before and after the collision, is ANGULAR momentum CONSERVED about this point? Lets call the point which connects the string and rod as P. Why am I asking this? : it is clear from the scenario that the point of concern, which connects the string and the rod, moves in a circular path due to the string...
View full post »
Thread 'A cylinder connected to a hanging mass'

Thread 'A cylinder connected to a hanging mass'

Let's declare that for the cylinder, mass = M = 10 kg Radius = R = 4 m For the wall and the floor, Friction coeff = ##\mu## = 0.5 For the hanging mass, mass = m = 11 kg First, we divide the force according to their respective plane (x and y thing, correct me if I'm wrong) and according to which, cylinder or the hanging mass, they're working on. Force on the hanging mass $$mg - T = ma$$ Force(Cylinder) on y $$N_f + f_w - Mg = 0$$ Force(Cylinder) on x $$T + f_f - N_w = Ma$$ There's also...
View full post »

Similar threads

How Are Beam Support Reactions Calculated?
Replies
3
Views
2K
Find the amount of work done against gravity in moving a 150kg rocket
Replies
4
Views
895
Calculate the work required to move the block
Replies
28
Views
4K
Force of water against a dam gate
Replies
29
Views
3K
Calculating work against gravity
Replies
5
Views
3K
At what distance does a seaplane's boundary layer transition to turbulence?
Replies
1
Views
2K
Calculating Gforce of Impact from 3ft Fall
Replies
2
Views
2K
Power drawn by a water pump to project water through nozzle
Replies
1
Views
2K
Regarding the work done against air resistance
Replies
2
Views
3K
Measurements Calculation Problem
Replies
3
Views
847

Hot Threads

Recent Insights

Back
Top