Why are the objects the same speed at the finish line?

Click For Summary
SUMMARY

The discussion centers on the physics principle that two objects, despite traveling different distances, can reach the same speed at the finish line due to equal net work done on them. The net work is determined by the gravitational force acting on both objects, as they move down a frictionless ramp. The normal force does not contribute to the work done since its component in the direction of displacement is zero. Thus, both objects achieve the same kinetic energy and final velocity at the finish line.

PREREQUISITES
  • Understanding of kinetic energy and its formula: KE = 0.5mv^2
  • Knowledge of work-energy principle and net work
  • Familiarity with forces acting on objects on an inclined plane
  • Concept of frictionless surfaces and their implications in physics
NEXT STEPS
  • Study the work-energy theorem in detail
  • Learn about the role of normal force in physics problems
  • Explore the implications of frictionless surfaces in mechanics
  • Investigate the effects of different forces on motion in inclined planes
USEFUL FOR

Students of physics, educators explaining mechanics concepts, and anyone interested in understanding the principles of motion and forces on inclined planes.

Lori
I have the problem below.

I know that net work is equal to the change in kinetic energy which is Wnet= 0.5mv^2-0.5mvi^2.I also know that the work by force of gravity is the same for both objects. I don't understand why the objects would be the same speed at the finish line.
20171029_144753.jpg
 

Attachments

  • 20171029_144753.jpg
    20171029_144753.jpg
    32.9 KB · Views: 420
Physics news on Phys.org
The speed will be the same. This does not mean that they will reach the finish line at the same time, block B has to travel longer.
 
Orodruin said:
The speed will be the same. This does not mean that they will reach the finish line at the same time, block B has to travel longer.
Can you explain why this would be the case? Would it be because net work is the same for both objects? Because if that's the case, then KE has to be the same and so the final velocities are the same.

However. I wouldn't know why new work is the same for both objects.
 
Lori said:
Would it be because net work is the same for both objects? Because if that's the case, then KE has to be the same and so the final velocities are the same.
Yes.

Lori said:
I wouldn't know why new work is the same for both objects.
You said it yourself in the first post:
Lori said:
I also know that the work by force of gravity is the same for both objects.
 
  • Like
Likes   Reactions: Lori
Orodruin said:
Yes.You said it yourself in the first post:
Ahh yeah. I wasn't sure if force of gravity was the only work done on object but it makes sense since the ramp is frictionless and gravity is the only force applied.
 
Lori said:
Ahh yeah. I wasn't sure if force of gravity was the only work done on object but it makes sense since the ramp is frictionless and gravity is the only force applied.
Gravity is not the only force. There is also a normal force from the ramp. Can you figure out why it does no work?
 
Orodruin said:
Gravity is not the only force. There is also a normal force from the ramp. Can you figure out why it does no work?
Oh . Well the component in the y direction of gravity balances out normal force. So the normal force doesn't do any work.
 
Lori said:
Oh . Well the component in the y direction of gravity balances out normal force. So the normal force doesn't do any work.
It is not really a matter of force equilibrium. Whether a force does work or not depends on the force's component parallel to the displacement.
 
Orodruin said:
It is not really a matter of force equilibrium. Whether a force does work or not depends on the force's component parallel to the displacement.
Oh right! I was talking about net work. So the work that normal force does is 0
 

Similar threads

High School Curious about the work - energy theorem
  • · Replies 8 ·
Replies
8
Views
2K
High School How does an object gain potential energy?
  • · Replies 54 ·
2
Replies
54
Views
6K
High School Conceptually understanding change in potential energy with 0 net work
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad How to calculate the kinetic energy of an object propelled by a magnet?
  • · Replies 15 ·
Replies
15
Views
1K
Undergrad How can we prove the kinetic energy equation
  • · Replies 2 ·
Replies
2
Views
1K
Undergrad Work Done/Energy Transferred in One Dimensional Collision
  • · Replies 5 ·
Replies
5
Views
2K
High School About verification on Kinetic energy and work
  • · Replies 16 ·
Replies
16
Views
3K
Undergrad Same old question, I still don't get it: E=1/2mv^2 - more E with V?
  • · Replies 41 ·
2
Replies
41
Views
4K
Undergrad Is Mechanical Energy Conservation Free of Ambiguity - follow up
  • · Replies 77 ·
3
Replies
77
Views
6K
Undergrad Relationship between Concentration of a Force and Energy Density
  • · Replies 11 ·
Replies
11
Views
2K