Can the kinetic energy of a system be negative?

AI Thread Summary
Kinetic energy cannot be negative, as it is calculated using the equation KE = 0.5 * m * v^2, where mass (m) and velocity (v) are squared, resulting in a non-negative value regardless of the direction of velocity. In contrast, gravitational potential energy can be negative because it is relative to a chosen reference point, allowing for values below that reference. The discussion emphasizes understanding the definitions of kinetic and potential energy to grasp these concepts better. The confusion arises from the interpretation of velocity's sign, but kinetic energy remains inherently non-negative. Understanding these principles is crucial for mastering energy concepts in physics.
parwana
Messages
182
Reaction score
0
Can the kinetic energy of a system be negative? Explain why or why not?

Also I know gravitational potential energy of a system can be negative but I need a better explanation on why it is so.
 
Physics news on Phys.org
What is the equation for kinetic energy? What about it helps you answer the question?

Potential energy (gravitational, voltege, etc.) is relative to some datum. How does that help you answer the 2nd question?


PS -- I'm moving this thread to the Homework forums.
 
It is best to look at the definitions, they provide good explanations. :smile:
 
I am just trying to understand the concept behind these. I guess Kinetic Energy can be negative if the velocity is negative. Also Potential energy can be negative due to g being negative.

Can someone explain these in greater details.
 
How can the KE be negative, given the simple form involving an object's mass and velocity?
 
by the way, if the velocity is negative, it doesn't make KE negative, since the equations for KE is (.5)(m)(v)^2. So if v is negative, it turns positive.
 

Thread 'Struggling to understand the concept of this question (ice cube in water optics question)'

TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
View full post »
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Similar threads

Conservation of Momentum Problem - Mechanical and Kinetic Energies
Replies
2
Views
957
Electric Potential Energy of Point Charge Systems
Replies
2
Views
940
Kinetic Energy of a Cylinder Rolling Without Slipping
Replies
21
Views
4K
Net work and kinetic energy (pushing a wagon to accelerate it)
Replies
1
Views
1K
Classic Incline problem with cylinder
Replies
13
Views
993
Energy conservation law question with capacitor
Replies
8
Views
2K
Work energy KE theorem for a book being lifted up in a gravitional field
Replies
18
Views
2K
Conservation of Energy with Gravitational Potential Energy
Replies
6
Views
2K
Determine energy required to stop rolling mass
Replies
10
Views
689
Challenging problem about an impact with a smooth frictionless surface
2
Replies
55
Views
5K

Hot Threads

Recent Insights

Back
Top