# mechanics

1. ### Angular Momentum

So to prove angular momentum (L = r x p) is conserved, I have to prove the derivative of L = 0. The proof I have is the derivative of L = (ṙ × p) + (r × ṗ) = 0 + r × F = 0 (Sorry about the formatting, really new here). I don't understand 1) Why (ṙ × p) = 0 2) Why r × F = 0...
2. ### Mechanics problem: ratios of velocities, times and distances

I am working through an old mechanics textbook for UK A-level (1970s/80s) and am having difficulty with following problem, which is from an old A-level paper. I have managed to solve the first part of the question, but am floundering on the second and third parts. Help please! This is the first...
3. ### Mechanics (M!) Motion Due to Gravity

Hi! I need help please! A particle of 0.5 kg is placed at a point O at an angle sin^-1(0.5) to the horizontal. It is projected up a track with a speed of 12m/s. There is a frictional force of magnitude 2N, which acts in a direction opposite to the direction of motion. a) Find the deceleration...
4. ### Complex projectile motion question

Consider a particle undergoing projectile motion where the particle has mass of 1/10 kg which is projected θ deg above the horizontal. So the particle is projected at a given point which is situated at the point where x = x0 and y = y0 (where x0 is unequal to 0, y0 is unequal to 0 and y = 0 is...
5. ### Mechanics: Circular Motion and Tension Question

Answer: Please could someone explain to me why in (ii) I double r, as it says in the answers.
6. ### Mechanics Ques ( M1)

The questions and answers are in the attachment! For No4 (iii) Since the stone is moving downward in the container and the resistance to motion acting upwards i did mg - R = ma But it did the inverse in the marking scheme , can someone explain me it ? For 5(i) i don't understand how to...
7. ### Mechanics Ques ( M1)

An object of mass 10kg slides down a plane inclined at 8° to the horizontal , starting from rest at the point A. The point B is a distance of 15m down the plane from A. The speed of the object when it reaches B is 5 ms. For the motion from A to B , find (i) the increase in the kinetic energy of...
8. ### Schrodinger Equation/Quantum Mechanics: Can't Normalize Wave Function

Hello. :) I've been looking over my notes on Schrodinger's equation, and I came across this example. It's dealing with particles passing through a finite square well. The potential energy is taken to be: V(x) = \left\{\begin{array}{lr}0 & : |x|<a\\V_0 & : |x|>a\end{array}\right. I'm to use...

Hello. I've been doing my differential equations coursework recently and I am so close to finishing it but I have one last bit I'm stuck on. The coursework aim is to model 2 equations, representing the velocity of an aeroplane that has just landed (at t=0). All we are given is a table of...
10. ### Engineering Mechanics, Finding angle Alpha

So I have a mechanics question 2.65 of which I have deduced the following : x-Component of all forces F1 = 150 cos30 F2= 150 cos \alpha F3 = 150 cos(\alpha+50) y-Components of all forces F1 = -150 sin30 F2 = 150 sin \alpha F3 = 150 cos(50-\alpha) Finally, R = \sqrt{(\Sigma Fx)^2 + (\Sigma...
11. ### Mechanics - projectile

I dont get this from the star sign. (Question above the star sign is fine) When i try to find external radii by substituting 60degree into Range equation, it gives me [(sqrt3)v^2]/2g instead of V^2/g which the question required. Also how do i do next part? (Deduce~~~)
12. ### Mechanics circular motion

Question. Answer. I dont get (iii) highlighted part (Iii) asks for a complete circle but why do we have to put a pie instead of 2pie? I know if i put 2pie, u^2 will be negative but why is the critical point(what is this) at pie?
13. ### Vertical circular motion - Mechanics 2

Small bead mass denoted by m, suspended from fixed point O by a light inextensible string length a. Then set into motion with the string taut at B where B is vertically below O which horizontal speed u. Given that the string does not become slack, show the least value of u required for the...
14. ### AQA A2 mechanics 2 help

Looking at AQA June 08 MM2B Q7a...Normally at the top of circular motion v is equal or greater than 0 for complete revolutions but somehow they have it equalling ag and it looks like they've disregarded the tension in the string at the top. If anyone can help me please....
15. ### Mechanics rigid objects in equilibrium

Q: A portable lamp consists of a uniform circular base with a perp pole through its centre. Its centre of mass is at a height h above its base. When it is placed on a sloping ramp, it is on the point of both sliding and toppling. A force is now applied parallel to the ramp to try to push it...
16. ### mechanics elastic springs

A new bulb with a bayonet fitting is to be inserted into a vertical lamp holder the mass of the bulb is 40gram. To insert the bulb it is first placed in the holder so that it rests on the two vertical springs it then has to be pushed down 6mm against the springs and twisted then when it is...
17. ### mechanics new question equilibrium

i was able to find that coefficient should be smaller than 0.3 but can't solve the toppling part answer is that coefficient is between 0.2 and 0.3
18. ### Mechanics rigid objects in equilibrium

answer for first part is 0.275
19. ### Mechanics problem centre of mass

i cant figure out as to how to solve part (ii) i know that i should take moments about O i also know that we should get 0.36 for the distance of centre of gravity from o for that hole but why are we taking the area of that thing that isnt there
20. ### Mechanics problem centre of mass

where k is the density of that material mass of cuboid 50*10*10k distance from x-axis= 5 mass of other cuboid 10*10*10k distance from x-axis=15...