Power particle-like object problem

  • Thread starter Thread starter critch
  • Start date Start date
  • Tags Tags
    Power
AI Thread Summary
The discussion revolves around calculating the instantaneous power exerted on a particle-like object under a specific force and velocity. The force is given as F = (5.0 N) i - (1.0 N) j + (10.0 N) k, while the velocity is v = - (2.0 m/s) i + (4.0 m/s) k. The user initially attempted to find the power by taking the dot product of the force and velocity but arrived at an incorrect result of 41.2 Watts. Other participants clarified that the dot product alone is sufficient for the first part, and for the second part, they suggested setting the velocity to only the j component and equating the product to the given instantaneous power of -12 W. The conversation emphasizes the importance of correctly applying the dot product and understanding the relationship between force, velocity, and power.
critch
Messages
1
Reaction score
0
Hi, I've been trying to complete this question for almost an hour, i was hoping you could provide some advice

At a certain instant, a particle-like object is acted on by a force F = (5.0 N) i hat - (1.0 N) j hat + (10.0 N) k hat while the object's velocity is v = - (2.0 m/s) i hat + (4.0 m/s) k hat. 1)What is the instantaneous rate at which the force does work on the object?

2)At some other time, the velocity consists of only a j component. If the force is unchanged, and the instantaneous power is -12 W, what is the velocity of the object just then?

I tried taking the dot product of the force and velocity, making sure i only multiplied the like terms of the unit vectors. then i took the hypotenuse using pythagoras, but the answer i get is 41.2 Watts and its not right? please could someone help?
 
Physics news on Phys.org
critch said:
I tried taking the dot product of the force and velocity, making sure i only multiplied the like terms of the unit vectors. then i took the hypotenuse using pythagoras, but the answer i get is 41.2 Watts and its not right? please could someone help?

1) Taking the dot product is enough. I didn't quite understand what you have done after that.

2) Suppose the velo is v = vj. Find F.v and equate it to the instantaneous power given.
 

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

What is the induced magnetic force on this closed current loop?
Replies
12
Views
2K
Are the 2nd and 3rd problems in this video correctly solved? (charged dipole and organ pipe problems)
Replies
3
Views
1K
Spherical ball rolling back and forth in a bowl
Replies
24
Views
2K
Electrodynamics: charge of a particle
Replies
25
Views
2K
Initial velocity of bird landing on horizontal wire modeled as spring
Replies
7
Views
974
Sign Convention for Angular Acceleration in Rotational Motion
Replies
15
Views
2K
How Do You Correctly Cancel Angular Momentum in Physics Problems?
Replies
3
Views
1K
Calculate Distance Traveled: Instantaneous vs. Average Velocity
Replies
5
Views
2K
Zero momentum reference frame and an inelastic collision
Replies
4
Views
3K
Avg Power in a Rotational Energy/Work Problem
Replies
6
Views
1K

Hot Threads

Recent Insights

Back
Top