The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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1
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2answers
190 views

How to find the height at which a projectile is launched from an angle? [closed]

I need guidance with the following question: A boat is $50.0m$ from the base of a cliff, fleeing at $5.00m/s$. A gun mounted on the edge of the cliff fires a shell at $40.0m/s$ and hits the boat ...
0
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2answers
3k views

Vertical motion initial velocity given max height

I'm having a hard time finding a formula that calculates the initial vertical velocity for a projectile that should reach a certain height. I'm using this formula to calculate both vertical and ...
1
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2answers
415 views

Half-atwood machine with accelerating pulley

This is a follow-up to my previous question, in which I am now trying to calculate the acceleration of the cart (as before, the block surfaces are frictionless). The mass $m_2$ is attached to $M$ via ...
-2
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1answer
36 views

Time in a vertical circular motion [closed]

How can I calculate the time taken to go from one point to another, in vertical circular motion? If we have radius, angle between 2 points, and initial velocity. I tried to write $\frac{dv}{dt} = g ...
-1
votes
2answers
88 views

Stone released from balloon [closed]

Q: If a stone is released from a balloon rising with acceleration a at the instant when its velocity is v. Then immediately after release the acceleration and velocity of the stone are ? I tried to ...
-2
votes
1answer
29 views

Using resultant vectors to calculate how long it takes to travel a distance [closed]

A box of books weighing $320 \;\mathrm{N}$ is shoved across the floor of an apartment by a force of $569 \;\mathrm{N}$ exerted downward at an angle of $36.5^\circ$ below the horizontal. The ...
0
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1answer
44 views

What's the average speed (along $z$) and the average position (along $z$) of an object in free fall?

I'm looking to calculate the average speed (along z) and the average position (along z) of an object in free fall. The initial instant is $t_0$ and we have: $z(t=t_0)=z_0$ $v_z(t=t_0)=v_0=0$ I ...
1
vote
1answer
76 views

Whether a large or a small ball fall faster in the air?

Given a ball falling under gravity is subjected to air resistance, after performing a differential to the drag equation, I get: $$g-Z(v^2)/r = a = v',$$ (where $Z$ is a constant.) How can I know ...
0
votes
1answer
24 views

Steps in a proof in kinetic equation of motion

This is a part of a kinetic equation of motion, \begin{align} x(t) - x_0 &= \frac{1}{2}a \left[ \frac{v(t) - v_0}{a} \right]^2 + v_0 \left[ \frac{v(t) - v_0}{a} \right] \tag{1.17} \\ &= ...
0
votes
2answers
139 views

Kinematic Problem, two balls thrown down from building at different times, when will they meet and what distance will they hit at? [closed]

You drop a ball from a building on the road $40\, \mathrm{m}$ below. Your friend beside you throws a second ball 1 second later at $25\,\mathrm{m/s}$, trying to hit your ball in mid-air. Assuming the ...
0
votes
0answers
101 views

Relative displacement of a point in a deformed object

I have a 3d model (nodes and elements) and it undergoes translation and rotation at different time steps Ti. I want to know the displacement relative to some point in the model which is kept as fixed ...
0
votes
1answer
37 views

Determine time over known distance, constant acceleration and starting speed [closed]

Problem: I have an object covering a specific distance (say 100m) at a starting speed (say 10m/s) and a constant acceleration of 1m/s/s. Which equation can I use determine how long it will take the ...
0
votes
1answer
33 views

How do I calculate the speeds in x, y, and theta of a spinning rod?

Suppose the object looks like the diagram below (it is the horizontal rod). On the vertices, are two velocity vectors $v_r$ and $v_l$. The question is: how is the motion of the rod affected by these ...
-1
votes
1answer
81 views

How can we apply Newtons laws, or kinematics to solve a problem like this one?

Problem: Two objects with masses 5.00 kg and 2.00 kg hang .600 m above the floor from the ends of a cord 6.00 m long passing over a frictionless pulley. Both objects start from rest. Find the maximum ...
1
vote
2answers
64 views

What is the physical significance of Rapidity in Relativistic kinematics?

Recently I have came across a new term called rapidity in relativistic kinematics. We are using it in relativistic kinematics due to its additivity whereas velocity is not a additive quantity in ...
4
votes
1answer
5k views

Why is the velocity on the top of a wheel twice the velocity of its axle?

When a wheel is rolling, not skidding, and its axle moves at velocity $\vec{v}$, then a point on the top of its circumference will move at velocity $2\vec{v}$, shown below. I really don't ...
2
votes
2answers
260 views

Pulley system on a frictionless cart

Let's say you have a pulley set up as below on a cart, with a massless pulley and string. The mass hanging off the side is attached via a rail, and all surfaces & pulley are frictionless except ...
-1
votes
6answers
268 views

What is the acceleration at the top most point of a ball’s journey vertically upward?

When i shoot a ball vertically upward, it’s velocity is decreasing. So there is acceleration. -9.8m/s^2. I’ve read that at the top most point, the acceleration is STILL 9.8 m/s^2 where v=0 . The ...
2
votes
7answers
965 views

Why is momentum conserved (or rather what makes an object carry on moving infinitely)?

I know this is an incredibly simple question, but I am trying to find a very simple explanation to this other than the simple logic that energy is conserved when two items impact and bounce off each ...
1
vote
1answer
90 views

Distance and velocity question

I know that speed is the derivative of distance. So integrating speed should give you distance. Let's suppose we have a speed which obeys this function: $$ v(x) = 2^{2^x} $$ So at time 0 the speed ...
0
votes
1answer
43 views

Velocity required for a car on a a frictionless banked surface

My textbook has clearly explained and derived a velocity that is required for a car to navigate a turn on a frictionless banked surface. I have understood it too. My doubt is about what happens when ...
0
votes
1answer
49 views

Why the point right below the center of a rolling ball on the ball has zero instantaneous velocity [duplicate]

Suppose there is a snooker ball rolling on a table. The velocity of the center of the ball is Rω and its direction is horizontally right. I don't understand why the point right below the center on the ...
0
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0answers
57 views

Disk Free falling in magnetic field

A circular metal plate starts falling from rest in a region of uniform magnetic field "B". B is parallel to the plane of plate and to the surface of earth(refer to diagram).The plate has mass "M" ...
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votes
1answer
54 views

Value of $g$ in projectile problems

A cannon has a muzzle speed velocity Vo of 60.0m/s, at what angle theta should it be aimed to strike a distance 320 meters away. Ignore air resistance So I get how to set this up but I am ...
2
votes
2answers
50 views

Does $v^2=v_0^2-2gh$ work if the positive axis is up and the initial velocity is down?

In the situation where the positive axis is up, the acceleration due to gravity is $g$, and the velocity is represented by the equation $v^2=v_0^2 - 2gh$. This works great if the initial velocity is ...
1
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1answer
76 views

Invariant mass spectrum to a transverse momentum distribution

For the decay of the Higgs boson in 2 photons having the following invariant mass formula: $$M = 2E_{1}E_{2}(1 - \cos \theta)$$ How can I go from an invariant mass spectrum distribution to a ...
8
votes
5answers
2k views

How to brake 'beautifully'?

Sometimes when I'm driving my car, I play a "game" against myself in which I try to minimize the deceleration felt by passengers (including myself) while still braking in a reasonable short space. I ...
3
votes
1answer
141 views

How is $ \frac{dv}{ dt} = a $?

I know how , in the physical sense - $$\frac {dv}{dt} = a$$ But, even after thinking a lot, I am not able to see the fault in this - $$\frac {dv}{dt} = \frac {d(st^{-1})}{dt} = \frac ...
0
votes
2answers
97 views

Kinematics with acceleration as a function of velocity

Say there is a particle moving at $50~\text{m/s}$ and modeled with a function of acceleration such that: $$a = - 0.5v$$ (this is derived from a force as a function of velocity) $$F = 50v = ...
1
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1answer
47 views

Why does everything written on a page appear in concentric circles when we rotate that page? [closed]

When i put a pencil in the middle of a paper and rotate it very fast, whatsoever is written on it, will appear in concentric circles. What is the reason behind this phenomenon and what is it called?
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votes
2answers
61 views

1D Kinematics problem [closed]

The position of a particle in meters moving along the x-axis is given by: $x = 3(t − 2)^2 − 12$ for $0 \le t \le 15$ How can I find the velocity of the particle when it is passing through the point ...
0
votes
3answers
401 views

Changing directions with a constant speed?

I'm currently working on a problem in which an object's speed remains the same, but it experiences a change in direction after some time. I'm fairly sure it experiences an acceleration in order to ...
0
votes
0answers
26 views

Rotational Velocity

I would like to calculate rotational velocity from Global(fixed frame of reference) in local (moving frame of reference). How to do that? i know the relationship between global and local frame of ...
-4
votes
2answers
55 views

Do I need to differentiate this equation or not?

I've been given this equation: $$\mathrm{velocity}, v = 2\,\mathrm{cm/s^3} \,t^2 + 5\,\rm cm/s.$$ If someone now asks me to tell the velocity at, say 4 sec, then before proceeding with the equation, ...
11
votes
5answers
648 views

What is the best path for a given initial and final state?

I am trying to calculate an efficient acceleration curve given starting and final positions and velocities. I'm assuming no friction, and that the acceleration can be applied in any direction at any ...
-1
votes
1answer
71 views

Is this an acceptable approach to solving the following problem? [closed]

Why does my approach not work for the following problem? PROBLEM A man stands on the roof of a building of height $14.6\,\mathrm{m}$ and throws a rock with a velocity of magnitude ...
0
votes
1answer
491 views

x-coordinate of the ball when it's velocity is perpendicular to projection velocity

We have a ball projected at 20 m/s at an angle $\pi/6$ from the x-axis. Now we have to calculate x-coordinate of the ball when it's velocity is perpendicular to projection velocity. I am thinking ...
1
vote
1answer
97 views

Derivation of Torricelli's equation

I am reading "Fundamentals of Physics" by Shanker and he is deriving Torricelli's equation. First he says $\displaystyle a = \frac{dv}{dt}$. Next, he multiplies both sides by velocity to get ...
0
votes
1answer
51 views

Zero net external force

Is it possible to have a changing kinetic energy when the resultant of the external forces on the system of particles is zero? According to my thoughts, if the net external forces are zero, the body ...
-1
votes
1answer
96 views

Minimum time taken by train to reach its station [closed]

A train starts from station A and reaches station B. It first accelerates at a rate € and then moves with constant velocity and then retards at a rate ¥.But suppose we are to calculate the minimum ...
0
votes
2answers
288 views

Finding acceleration and distance when velocity given

I am trying to do the following question for practice (it is an interview question), and I don't know if my methods and answer are correct. Given a velocity $v=2+3t^2$, find acceleration after 3 ...
5
votes
2answers
265 views

How is Chasles' Theorem true?

Chasles' Theorem in its strong form says: The most general rigid body displacement can be produced by a translation along a line (called its screw axis) followed (or preceded) by a rotation about ...
0
votes
1answer
47 views

Optimal Firing Rate to Maximize Vehicle Velocity

Suppose that you are in a vehicle in space with a power source generating a constant power of $P_0$ that you can use to fire iron pellets. The iron pellets compose 99% of the ship's mass, $m$. The ...
2
votes
1answer
114 views

Does a rotating object have more inertia, mass and gravitational pull?

When an object is rotating on an axis, it has stored rotational energy in it. Since energy and mass are related, does this stored rotation increase the mass of the object? And if so, will it be harder ...
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votes
2answers
82 views

Why the bob leaves the circular path when tension in the string becomes zero [duplicate]

In vertical circular motion of a bob attached with a string, we say that the bob leaves the circular path when tension in the string becomes zero. But even when tension becomes zero there's ...
0
votes
1answer
64 views

Why is drag neglected while dealing with kinematic problems?

Why is drag neglected while dealing with kinematic problems? While dealing with problems related to finding velocity, acceleration and other kinematic problems, it is mentioned to "neglect drag". ...
3
votes
4answers
8k views

Maximum range of a projectile launched from elevation “dumbed down”

I am trying to conceptually understand why the angle which produces the greatest range for a projectile launched with an elevation is not 45 degrees. I have exausted all other options, and I hope that ...
1
vote
3answers
325 views

Can the force acting on a body remain constant if the body is accelerating?

Since $F=ma$, the force should change if acceleration changes shouldn't it? And since acceleration is the rate of change of velocity, can velocity be constant if acceleration changes?
1
vote
6answers
406 views

Why is there a universal speed limit?

I am looking for an answer that does not rely on Special or General Relativity -and without recourse to the fact that the speed of light is frame invariant. Is there another way of showing this ...
3
votes
0answers
135 views

Free-Fall Lab Help - Getting weird results

So, I am doing a free-fall lab for my physics class. We got the values and I have the results here(we used a infrared photo-gate). Basically, we have a brass cylinder and a wood cylinder. Each are ...