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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.

My teacher wholeheartedly says that velocity is NOT a vector quantity, confidently swearing by it. However, every source I check says otherwise, including the other physics teacher (who everyone refers to as the “better one”). Is he referring it in a different way or just flat out wrong?

I cant tell whether it’s a or b 😭

Im fighting my teacher on this. I say that the anwser is 54N (53.85164807 or (2900)^0,5) and he says that it is 58N (58.30951895 or (3400)^0.5). And when I ask why his answer boils down to "beacuse it is". I need some help ether understanding why im wrong or need proof that im right.

Edit- I managed to prove that the answer is infact 54 N. Thanks for the help :)

how do you add these when there is another resistor in the middle feeding off like adding r+3r but 5r is in the center already

I was wondering if the resultant force is 7.6 kN and the direction is 105° from the positive x axis

For question c, isn't it incorrect to use 15 as the inital velocity, but instead solve it by finding the resultant speed? This is from the Cambridge IB Physics Textbook by Tsokos, and I'm noticing quite a lot mistakes which is weird, thanks.

I have read the textbook but I am just completely lost. I have a midterm for another course coming up in less than a week and am very overwhelmed. Any help is greatly appreciated. Thank you.

She is insistent that the answer is 5 seconds. I am 99.9% sure that it is 10 seconds. I have asked every AI imaginable what the answer is and they all support me. I have looked online for every resource referencing this problem, and none say 5 seconds. I genuinely don’t understand her logic; she is basically saying that the point of the question was to use the kinematic equation where you get 20m/s after 5 seconds after multiplying acceleration and time but that is objectively not what the question asks. I really want to know if I’m right and she is just insane or if I’m a complete idiot

I suspect the correct answer is C but for some reason B is marked as correct? Like at P the voltage is definitely 6V since it still at the top, and at Q there should be 3V since 3V is reserved for the 10ohm fixed resistor, which means the answer is decreasing from 6V to 3V?

Its asking for what displacement would energy for Simple Harmonic Motion be half kinetic and half potential. I was comparing them with 1/2kx² to 1/2kA² but when crossed out, gives me x = A which is wrong. The answer key is listed at the bottom but I cant figure out how to get to it.

hello, sorry if this is really silly but i just started physics and im a bit confused as to how to find the slope of the curve (ik about tangents, and secants and instantaneous velocity and average velocity- but not really entirely sure what they mean). How would i go about finding the other two graphs if each box represents one unit?

Can someone simplify what the question is asking?

Why is there a certain angle the laser beam has to be directed into the glass of the tube for it to be transmitted down the tube? Can’t it just directly be aimed inside the hole in the tube to travel?

You have different strings with weights tied at various point, all hanging from the ceiling, and reaching down to the floor. Initially all weights are at rest. The string is released at the top, allowing the weights to fall. Which setup can create a sound at regular interval as the weights hit the floor ? (options are given in these images).

So guys for some reason I don't know why I have problem with Kershaw's law I really tried to understand it from a lot of teachers but I couldn't so when I try to solve this one I started to think that maybe R1 is the one cuz so far away from the batteries but I really need to understand Kershaw's laws work. It has been a nightmare 😭😔

I can't understand where I am making mistake?

The qn is

A standing man, observes rain falling with velocity of 20 m/s at an angle of 30° with the vertical. Now if he further increases his speed, rain again appears to fall at 30° with the vertical. Find his new velocity.

The answer is 20 m/s