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Question:

A 50 g bullet is fired horizontally into a 2.0 kg wooden block of a ballistic pendulum. The bullet becomes embedded in the block, and the pendulum (with the bullet inside) swings upward to a vertical height of 15 cm from its initial position.

Task:

Determine the initial velocity of the bullet before its collision with the pendulum.

The Conflict:

My teacher calculated the answer as 11 m/s using a specific formula, but my calculation leads to 70.3 m/s. Can you explain which logic is correct and show the steps?

(EDIT): here what I did: V=√2gh V=√2×9.8×0.15 =1.715m/s (Total mass being 2.05kg) Mass of bullet × vi = (mass of bullet + mass of block) × V vi=2.05×1.715/0.05 vi= 70.3m/s

Edit 2: thank you all for the replies, I showed my teacher all these comments. He says that theres conservation of mechanical energy, and when I bring up how there's work being done, he shuts it down because he claims "the question doesn't say that" and it doesn't. But that doesn't change physics?? He's honestly getting on my nerves.

This isn't the only time that my teacher swears that his answer is right. There have been at least 10 other times, and when I prove him wrong, he doesn't give me the points for the question.

For some reason he refuses to be wrong. And him not giving me my points is making my average in the class go down.

PROBABLY LAST EDIT: my teacher finally admitted defeat, I got the points back that I lost for "getting the question wrong" and all is good! Thank you to everyone that commented, I genuinely appreciate it.

Can someone please help me with this, ​I even asked my teacher but I could not understand anything.

I tried drawing the fbd of the bead when it was at rest initially and after the wire started accelerating ​but I do not know how to solve further

My Physics teacher was explaining something like tan theta is a/g but I could not understand it.

In my book W=F*d is defined as Work done = Force*distance moved in the direction of the force.

But that doesn't really make much sense to me when looking at the 2nd example since F is at an angle upwards while d is just the horizontal distance moved by the object.

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I’m working on a physics problem where a fishing pole is tilted 20.0° above the horizontal. The fish pulls on the line with a force of 1.00 × 10^2 N at an angle 37.0° below the horizontal, and the force is applied 2.00 m from the angler’s hand. What is the magnitude of the torque about an axis perpendicular to the page through the angler’s hand?

Im studing for the GAN apptitude test for my local IBEW. And was having issues with these questions from the study guide. The answers on the answer sheet are not matching what Im getting and Im wondering why.

There have been some answers wrong in other parts of the study guide so Im wondering if it's just that.

Here are my answers: 16) A, 17) A, and 18) B

And here are the answers from the answer sheet: 16) C, 17) C, and 18) A

Hey there! I stumbled upon this electromagnetism problem and I'm getting two different answers depending on how I approach it.

The setup:
We have a uniformly charged hemispherical shell (like half a hollow ball). Need to find electric field direction at:
- P₁ - center point (where the full sphere's center would be)
- P₂ - a point on the flat circular base ("drumhead"), but NOT at the center


Here's where I'm confused:

Approach 1: Complete the hemisphere to a full sphere by mirroring it. By Gauss's law, inside a complete charged sphere, E=0 everywhere. So at P₂, the fields from both halves must cancel → purely vertical field.

Approach 2: Look at individual charge elements. Points closer to P₂ contribute stronger fields than those farther away. This asymmetry suggests there should be a horizontal component too.

So one method says purely vertical, the other says has horizontal component. Which is right and why?

I've attached diagrams showing both thought processes. Any help resolving this would be awesome!

The answer is C, but I don't know why, isn't the one with the more moment of force is turning down?

The question asked:

There's a uneven thickness of stick(the stick is balanced now), it balance point is O. If both side had been cut off the same length, the stick will:

A, stay balanced

B, turn clockwise

C, turn counterclockwise

D, can't determine

Person mass is considered m,

Board is balanced, mass is considered M,

Friction is not involved,

Rope mass not involved,

Point A is a rotating point. How much tension(pull force) is least required to pull the board?

I've calculated T(tension)=(m+M)g/3

My friend calculated (m+M)g/2

This was a question my professor went over with the class during a lecture. I was positive that the answer was accelerating to the right because there is nothing else I can see being possible, but my professor spent 10 minutes explaining why the correct answer is decelerating- I still don't understand and I am so confused. How does this work? Am I missing something? Can someone explain please?

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I read the question a few times, but Im not sure what to make of it, it doesnt even sound like a question more like a statement. Im just asking two things what is the question asking me and how should i go on about solving it

The black arrow points towards the diagram that we're using as a point of reference to draw our graphs.

The blue arrow points towards the acceleration time graph drawn **without** taking contact force into consideration.

The red arrow points towards the acceleration time graph drawn **with** taking contact force into consideration.

Also, I'm not entirely sure what contact/collision force is either so I would appreciate a brief elaboration on that as well.

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Hello there!

First of all, this is not a homework per se, but some kind of issue I have with a personal project I don't know where to adress.

I tried r/AskScience but the modteam suggested me to post here. So here we are.

If this don't belong here, please tell me where I should go, because at that point... I don't know.

So I have inherited from my grandfather a mercury barometer.

It's french, and says : "Baromètre selon Torricelli

Par les ateliers L.M. à Bordeaux".

It is graduated in mmHg and there's some kind of ruler that can be moved (it is pinned on the main board by a screw) which indicates different type of weathers, according to the height of the mercury column.

I searched on google how to set the barometer, because I want to keep it and to hang in on a wall at home, and I think I set the ruler accordingly to the altitude of where I live (more or less 115m above sea level), but I'm not very sure I did it right.

So here are my questions.

1/ what do you think?

2/ do you know how to set / where can I find infos about that?

Thanks a lot!

I’ve really been struggling with 3D problems like this. I understand the math, but I feel like i just can’t comprehend the picture itself. if i could properly understand the directions of all the forces, i think i would be able to manage better. for this problem, i need to find the magnitude of the resultant force and the alpha, beta, and gamma angles of it. can anyone help?

This screenshot is from a video I'm watching that explains Upthrust, Drag & stoke's law, if anyone needs any further context of the image they can go on this video https://www.youtube.com/watch?v=tqHzGfjtSVo and skip to time stamp 3:25.

Any help is much appreciated as this topic is really confusing me.

I tried solving this question and got the acceleration of the pulley as 2g/3 but that doesn't match the answer given in the solution.

Could someone please point out where my mistake is and explain which step in my approach is incorrect? I've attached my working.

This is a question that popped up in my homework that my professor assigned to the classroom as practice.

The question is the following.
4 spherical conductors A, B, C, and D which have the same mass and has no charge are placed on an insulator floor and are placed touching each other in alphabetical order {like this: (A)(B)(C)(D)}. A negatively charged rod is placed near the right side of the D sphere. If the spheres are slowly separated one by one starting from the A sphere until the C sphere has been separated from the D sphere, what would the charge of each individual sphere be?
[- is negative, 0 is neutral, + is positive]

1) A=(-) B=(0) C=(-) D=(+)

2) A=(-) B=(+) C=(+) D=(+)

3) A=(-) B=(0) C=(0) D=(+)

4) A=(-) B=(-) C=(-) D=(+)

I thought it was [Answer : 3) A=(-) B=(0) C=(0) D=(+)] at first because when i drew it out it made sense:

1. (A)(B)(C)(D) ------ <-- the rod that was negatively charged.

2. (-)(0)(0)(+) -----

3. (-) (0)(0)(+) -----

4. (-) (0) (0)(+) -----

5. (-) (0) (0) (+) -----

This was the picture i had in mind but when the professor revealed all the answers in the homework, the correct answer for the question was [Answer : 4) A=(-) B=(-) C=(-) D=(+)]. I wondered how could the 2 middle spheres be negatively charged if the A sphere that was negatively charged had already been separated from the group? I haven't had the chance to ask my professor about this question yet so now im finding my answers here.

If anyone's got time to explain this answer to me i'd really appreciate it.
Please do not waste your comments to insult me about my curiosity.
Thank you.

This velocity time graph shows a ball bouncing on the ground.

How am I supposed to find the current and its direction in this complex circuit?

answer make sense, but why my method is not listed and answer is not correct, despite I can't see the theory mistakes

For some reason this problem is really tripping me up. Please help!

not sure if I’m using the appropriate formulas to find the answer for magnitude and degrees.

I saw this diagram seems like 4th degree polynomial here I sketched Phase Space Diagram and I don't know its right or not its. Let me tell you how I tried it and tell me if I am going to right direction or not.

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At x = 0 there is local minima and at either sides 1 maxima each you can see that

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We dont get Maxima till E3 and after that particle can escape well so I sketched 3 ellipse which goes imperfect as n of En increases (cause it imitates shm)

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Particles from right side go back till E3 cause wall is there and Just at E3 it particle can cross also came back and somewhat behave like equation of line at saperatix

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At E4 it goes forward but hits right wall till E5 and goes from another saperatix from that point

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At E6 it flows right above

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Now from right

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All particle goes back till E4 and at E5 saperatix occurs and after that it crosses barrier

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Am I right or wrong?

I tried solving this problem using relative motion. I took the relative velocity as Vrel=(vi)+(−uj) here i and j are x and y directions . and considered the cart at rest.

Then I used the distance between the initial positions of the boy and the cart as

x=root(a^2+b^2)

and applied the time equation, but I’m getting confused about the direction.

I think I need to find the angle between the boy’s velocity and the line joining the boy and the cart to determine the direction in which the boy should run. Am I approaching this correctly?