Please refer to the attachment for a full solution.

1. What is work: When a force is applied on a body, it may or may not move depending upon the magnitude of the force and mass of the body. For example, if one tries to push a massive rock, it will not move. The person trying to push gets tired and we will concede that he did do work, albeit unsuccessfully. However, in study of mechanics, work is said to have been done by the force on the body only if the body moves. No work is done if the body does not move.

2. Magnitude of work: The magnitude of work done by the force F in causing a displacement s is defined as the product of the displacement and component of the force in the direction of the displacement.

Since displacement s and force F are vectors, by the definition of scalar (or dot) product, work W can also be expressed as W = s . F

Work done is a scalar quantity.

3. Units of Work: ...

Solution Summary

In this write-up the concept of Work, Energy and Power has been explained. Various types of mechanical energy, principle of conservation of mechanical energy etc. have also been explained with the help of examples.

"A 48.5 kg student climbs a 5.90 m long rope and stops at the top. What must her average speed be in order to match the power output of a 140 W lightbulb?"
Here's how I approached this problem:
Since 1 W = 1 J/s, I set KE = 140 J.
Then, v^2 = KE/((.5)m) = 140/24.25 = 5.77
Then v = 2.4 m/s
But that's not the right an

1) an object initially at rest reaches a velocity of 30m/s in 6 seconds, how much work is done during this time interval?
2) a roller coaster car with a mass of 1000kg starts at ground level and reaches a maximum height of 128m. what is the change in potential energy for the car? I f all the potential energy is turned into ki

Physical science (8th edition) by Bill W. Tillery
Parallel Exercises
1. How much work is done when a force of 800.0 Ni s exerted while pushing a crate across a level floor for a distance of 1.5m?
2. A force of 400.0 N is exerted on a 1,250 N car while moving it a distance of 3.0 m. How much work was done on the car?

Conservation of energy requires that the sum of the power absorbed by all the elements in a circuit be zero. The following Figure shows a circuit. All of the element voltage and current are specified. Are these voltages and currents correct?
Hint: Calculate the power absorbed by each element and add them up.
Work out the

I'm having a diffucult time understanding free energy vs activation energy
are they the same?
I know free energy is the portion of a system's energy that is available for work
but what is this compared to the activiation energy?

You are standing 2.2 m from a 150 W light bulb.
(a) If the pupil of your eye is a circle 5.1 mm in diameter, how much energy enters your eye per second? [Assume that 5.0% of the light bulb's power is converted to light.]
(b) Repeat part (a) for the case of a 2.2 mm diameter laser beam with a power of 0.66 mW.

Choose one alternative fuel (natural gas, electricity....) and describe in detail what will have to happen for it to become a significant energy supply source. Explain whether you believe this will happen. Analyse the promise and challenges associated with this supply source.
Please, give references.