Please Check to See if I'm Doing Work-Energy Problem Correctly

  • Thread starter Thread starter petern
  • Start date Start date
  • Tags Tags
    Work-energy
Click For Summary
SUMMARY

The discussion focuses on solving a work-energy problem involving a child on a bicycle with a total mass of 40 kg, ascending a hill 10 m high and 100 m long at an initial speed of 5 m/s, while experiencing a frictional force of 20 N. The correct approach involves applying the work-energy principle, where the initial kinetic energy (KE) and potential energy (PE) are balanced against the work done by friction. The final velocity at the bottom of the hill is calculated to be 11 m/s, confirming that the initial calculations and application of energy equations were accurate.

PREREQUISITES
  • Understanding of kinetic energy (KE) and potential energy (PE) equations
  • Familiarity with the work-energy principle
  • Basic knowledge of forces and friction in physics
  • Ability to manipulate equations involving energy and work
NEXT STEPS
  • Study the work-energy theorem in detail
  • Learn about energy conservation in mechanical systems
  • Explore the effects of friction on motion and energy
  • Practice solving similar problems involving kinetic and potential energy
USEFUL FOR

Students studying physics, particularly those focusing on mechanics and energy concepts, as well as educators looking for examples of work-energy problems in a practical context.

petern
Messages
89
Reaction score
0
[SOLVED] Please Check to See if I'm Doing Work-Energy Problem Correctly

Homework Statement



A child riding a bicycle has a total mass of 40 kg. The child approaches the top of a hill that is 10 m high and 100 m long at 5 m/s. If the force of friction between the bicycle and the hill is 20 N, what is the child's velocity at the bottom of the hill?

Homework Equations



K = 1/2 * mv^2, U = mgh, W = delta E, W = Fx * cos(theta)

The Attempt at a Solution



Can someone check to see if I'm doing this correctly. I think what they're trying to say is that you're already at the top.

I would first do K-initial + U-initial = 4420 J. Then Then set that to Fx and solve for F which is 44.2 N. Subtract 20 N from that and you get 24.2 N and multiply it back by x which gives you 242 J. Set that to K-final and solve for v and you get 11 m/s.

Did I do everything correctly?
 
Last edited:
Physics news on Phys.org
Use the energy equation properly. What you have written seems complicated to me. Where is cos theta comin from?

KE at bottom = KE at top + PE at top + Work done against friction.
 
I get 11m/s as well and I used the kinematic equations. So I guess you've done everything correctly.
 

Similar threads

Work done during a collision -- Change in Kinetic Energy & change in Momentum
  • · Replies 1 ·
Replies
1
Views
2K
Questions Regarding a Cat Going Up a Ramp
  • · Replies 56 ·
2
Replies
56
Views
5K
Calculating Work and Change in Thermal Energy
  • · Replies 2 ·
Replies
2
Views
2K
Is this work-energy theorem for a system correct?
  • · Replies 12 ·
Replies
12
Views
3K
Avg Power in a Rotational Energy/Work Problem
  • · Replies 6 ·
Replies
6
Views
2K
What is the problem with the units in this state equation of a gas?
  • · Replies 12 ·
Replies
12
Views
2K
Work done by gravitational force (new problem)
  • · Replies 9 ·
Replies
9
Views
3K
How much work, speed and distance
  • · Replies 15 ·
Replies
15
Views
5K
Projectile Motion : Work and Energy
  • · Replies 4 ·
Replies
4
Views
2K
Problem with solving for force constant k of spring?
  • · Replies 3 ·
Replies
3
Views
2K