Recent content by kuruman

Wordle 1,043 3/6 ⬜🟧🟦⬜🟦 ⬜🟧🟧🟧⬜ 🟧🟧🟧🟧🟧

Perhaps, but once you've seen it you know to use it next time. It's no different from the assumption you have to make in the case of a ballistic pendulum that the bullet embeds itself instantaneously and the bullet + block system starts moving from rest. After all, a completely inelastic...

Energy is not conserved because there is an explosion which releases additional mechanical energy. You see that in what you call the energy conservation equation. It says that the total kinetic energy of the fragments immediately after the explosion is twice the kinetic energy of the projectile...

Good question. Part of the mechanical energy is converted into heat, vibrations, sound, etc. more generally internal energy of the system. In this example, if you consider yourself raising the object as part of the system, then there is negative change in biological energy of the system. You...

Gravity is an external force acting on the projectile in the vertical direction.

The drawing is misleading. It shows two arrows labeled ##\dot x##, one on the wedge and another to the right of the sliding block. The first arrow clearly represents the horizontal velocity of the wedge relative to the ground. The second arrow is meant to be the horizontal velocity of the...

You missed my point. First of all, "doing work" is an incomplete and ambiguous statement without prepositions. You need to specify what force is doing work and on what system. The correct form is "Force F does work on system S" or "Work is done by force F on system S." Whichever way you...

I looked. The answer is 42.

Isn't 137 approximatey 1,876,900% of the fine structure constant's actual value?

I assume that by system you mean the two component system of Earth + object. In that case, the total energy of the system is mechanical, i.e. kinetic ##K## which is the sum of the kinetic energies of the two components and potential ##U## which depends on the spatial configuration of the two...

Wordle 1,042 3/6 ⬜⬜🟦⬜⬜ ⬜🟦⬜⬜⬜ 🟧🟧🟧🟧🟧

I think that adherence to the sign convention is not the teacher's problem here but unrecognized self-contradiction is. Teacher says "There is an upward Force and a downward Force." Furthermore, the diagram in the teacher's email shows the drag and weight forces in opposite directions. This is...

You are correct. Your teacher seems to be confused about how Newton's second law works. From the diagram in the email and using the convention that "up" is positive, the net force is ##F_{net}=F_D-mg=F_D-79~(\text{kg})\times 9.8~(\text{m/s})^2.## Mass times acceleration is positive (up)...

It's hard to tell what you're doing when you put down numbers without units. Is this the volume of all the logs together? What's the definition of density? If V = 3.94 (units TBA), what does V stand for in the equation above and how did it become 997? Where did this 997 come from anyway?

Wordle 1,041 3/6 ⬜⬜⬜🟦⬜ ⬜⬜🟦🟦🟧 🟧🟧🟧🟧🟧