An 800-n billboard worker stands on a 4.0-m scaffold supported by vertical ropes at each end. scaffold weighs 500-n and the worker stands 1.0 m from one end, what is the tension in the rope farther from the worker? (a) 1300 n (b) 1800 n (c) 450 n (d) none of these.

Explanation and

This problem is best answered by drawing a figure as a first step.

ABC is the scaffold.

A downward force of 500N is applied downwards at 1m from end A.

The weight of 800N is exerted by the scaffold uniformly distributed between A & C.

At A and C, ropes are attached to support the load.

Let Fc=tension in rope passing through C.

Take moments about A:

Fc = (500N * 1m +800N*(3+1)/2m / 4m

    = (500 Nm + 1600Nm) / 4m

    = 2100 Nm / 4m

   = 525 N

carbon is found in all living things. carbon atoms move constantly through

living organisms, the oceans, the atmosphere, and the earth’s crust in what is

known as the carbon cycle. the directions taken by carbon atoms through this

cycle are very complicated and can take millions of years to make a full circle.

all animals, from humans to the dinosaurs are part of the carbon cycle. when

animals eat food, they get carbon in the form of carbohydrates and proteins.

in animals, oxygen combines with food in the cells to produce energy for daily

activity and then gives off carbon. the carbon combines with oxygen to form

carbon dioxide (co2) and is released back into the atmosphere as a waste

product when animals breathe and exhale.

from 145-65 million years ago, earth was much

hotter than today and covered with dense,

tropical swamp forests. the trees and other

plants were immense and

provided an endless supply of

food for the giant animals that

roamed the land. somewhere in

the air above one of these

forests, a lone carbon atom has joined

up with two oxygen atoms to form a molecule of co2.

the co2 molecule was sucked into the tiny holes (stomata) on the leaf of a

fern plant and joined with sunlight, chlorophyll and water to make food and

energy in the plant’s cells through photosynthesis. the oxygen (o2) from the

co2 molecule was sent back into the atmosphere; the carbon atom (c) was

detached and used to make a molecule of sugar.

if that carbon atom had been eaten instead, a totally

different situation would have developed. let’s say

that a giant plant-eating dinosaur (herbivore) ate the

fern for breakfast, and swallowed the carbon in the

fern in the form of carbohydrates and proteins. in

the process of respiration, oxygen combined with

the carbohydrates and proteins in the dinosaur’s cells

to provide energy for its daily activity.  

it has to be b, about 97 percent.