Net work and kinetic energy (pushing a wagon to accelerate it)

AI Thread Summary
The discussion centers on the confusion regarding the use of work versus net work in calculating kinetic energy for a wagon. The original poster questions why their teacher used 500J of work instead of the 300J of net work they calculated. It is clarified that the net work done on the wagon corresponds to the change in kinetic energy. The impact of friction is acknowledged, as it does affect the wagon's acceleration, but the kinetic energy equation focuses on the net work applied. The importance of specifying the mass of the wagon for accurate calculations is also highlighted.
aqryus
Messages
6
Reaction score
1
Homework Statement
Bill does 500J of work on a wagon, friction does work of -200J. What is the final speed of the wagon if it starts at rest?
Relevant Equations
w=fdcostheta
Ek=1/2mv^2
I'm a little confused because my teacher used Bill's 500J of work for the kinetic energy equation and I don't understand why. I used the net work, so 300J, to find the speed and I'm not sure why that's wrong. Wouldn't friction make the wagon move slower than if there was no friction? So why isn't that accounted for in the kinetic energy equation to find speed? Thank you
 
Physics news on Phys.org
You are correct. The net work done on the wagon equals the change in the kinetic energy of the wagon. What did you get for the answer? Was the mass of the wagon specified?
 
Thread 'Minimum mass of a block'

Thread 'Minimum mass of a block'

Here we know that if block B is going to move up or just be at the verge of moving up ##Mg \sin \theta ## will act downwards and maximum static friction will act downwards ## \mu Mg \cos \theta ## Now what im confused by is how will we know " how quickly" block B reaches its maximum static friction value without any numbers, the suggested solution says that when block A is at its maximum extension, then block B will start to move up but with a certain set of values couldn't block A reach...
View full post »

Thread 'Electric field due to charges between 2 parallel infinite planes'

TL;DR Summary: Find Electric field due to charges between 2 parallel infinite planes using Gauss law at any point Here's the diagram. We have a uniform p (rho) density of charges between 2 infinite planes in the cartesian coordinates system. I used a cube of thickness a that spans from z=-a/2 to z=a/2 as a Gaussian surface, each side of the cube has area A. I know that the field depends only on z since there is translational invariance in x and y directions because the planes are...
View full post »
Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Thread 'Calculation of Tensile Forces in Piston-Type Water-Lifting Devices at Elevated Locations'

Figure 1 Overall Structure Diagram Figure 2: Top view of the piston when it is cylindrical A circular opening is created at a height of 5 meters above the water surface. Inside this opening is a sleeve-type piston with a cross-sectional area of 1 square meter. The piston is pulled to the right at a constant speed. The pulling force is（Figure 2）： F = ρshg = 1000 × 1 × 5 × 10 = 50,000 N. Figure 3: Modifying the structure to incorporate a fixed internal piston When I modify the piston...
View full post »

Similar threads

Work and Energy on a Slope - How Does a Block Move Up with Zero Net Work?
Replies
3
Views
2K
Work done during a collision -- Change in Kinetic Energy & change in Momentum
Replies
1
Views
2K
Work energy KE theorem for a book being lifted up in a gravitional field
Replies
18
Views
2K
Friction and an object stopping
Replies
12
Views
3K
Kinetic Energy of a Cylinder Rolling Without Slipping
Replies
21
Views
4K
Combined Rotation and Translation of a Rectangular Plate
Replies
9
Views
2K
Finding kinetic energy and initial velocity of a cart over time
Replies
6
Views
2K
Minimal rotational kinetic energy for a gyroscope to precess
Replies
33
Views
2K
Conservation of Momentum Problem - Mechanical and Kinetic Energies
Replies
2
Views
942
Questions Regarding a Cat Going Up a Ramp
2
Replies
56
Views
4K

Hot Threads

Recent Insights

Back
Top