This document entails a summary of information about Work, Power and Energy Theorem including definitions, diagrams and additional information to ensure an understanding of the concepts. An additional completed example of a question is included with a thorough explanation. These questions will chal...
WORK-ENERGY THEOREM
Work is done on an object when the object moves in the same plane as the force.
If a force is applied to an object at 90o to the motion of the object then that force does no
work on the object.
When a force is applied at an angle (θ) to an object then then work is done by the
component of the force that causes the object to move.
This is given by the following equation: 𝑊 = 𝐹∆𝑥𝑐𝑜𝑠 𝜃 W = work done (J)
o F = force applied (N)
o Δx = displacement (m)
o θ = angle of force to the direction of motion
Work is a scalar quantity therefore it has magnitude but not direction.
Work can be a negative value when the energy of the system decreases and positive when the
energy of the system increases.
Net work on an object can be calculated by applying the definition of work to each force acting on
the object while it is being displaced and then adding up each contribution.
Example
Calculate the net work done on a box of 50 kg which is being pulled by a 100 N at an angle of 250 to
the horizontal for 20 m while experiencing a frictional force of 10 N.
Answer
F = 100 N θ = 25o 𝑓 = 10 N Δx = 20 m
𝑊𝐹 = 𝐹∆𝑥𝑐𝑜𝑠 𝜃 = 100 20 (cos 25°) = 1812,62 𝐽
𝑊𝑓 = 𝑓∆𝑥𝑐𝑜𝑠 𝜃 = 10 20 (cos 180°) = −200 𝐽
(Friction always acts at 180o to the direction of motion)
𝑊𝑛𝑒𝑡 = 𝑊𝐹 + 𝑊𝑓 = 1812,62 + −200 = 1612,62 𝐽
The net work done on an object can also be calculated by first calculating the net force acting on
the object and then applying the equation.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller fatimakarjieker. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $3.01. You're not tied to anything after your purchase.
