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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1answer
180 views

Rocket projectile motion problem [closed]

I'm not really sure where to start with this question: In a brisk wind from the south-east of $14.1\:\mathrm{m/s}$ a rocket pointed due north is launched from a cliff that is $500\:\mathrm{m}$ above ...
1
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2answers
523 views

Instantaneous Centre of Rotation

Let's say a body is undergoing both rotational and translational motion. I know that ICR of the body as a whole will be the point about which the body is doing pure rotation, so basically will be the ...
-1
votes
1answer
35 views

Calculate the distance of a falling object and terminal speed [closed]

I have a homework problem that I would like to verify that I am doing it correctly. If anyone could help me see where I'm going wrong with the steps, I would really appreciate it. (a) Consider a ...
0
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1answer
75 views

Why does $v^2=cad$ by dimensional analysis rather than $v^2=ad$? [closed]

Constants are generally added in functions to adjust for when magnitudes don't contain information necessary to the accuracy of the equation. Why is it that $v^2=cad$ instead of $v^2=ad$? What ...
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1answer
45 views

I do not know whether i have solved this correctly. Can anyone help? [closed]

A cart is moving along the $x$-direction with a velocity of $4 \;\mathrm{m/s} $. A person on the cart throws a stone with a velocity of $6 \mathrm{m/s}$ relative to himself. In the frame of ...
1
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2answers
196 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
votes
1answer
53 views

Differential equation for velocity regarded as a function of distance [closed]

Given a differential equation for velocity, $dv/dt + v = 1$, as well as its solution, is it possible to derive a differential equation for velocity with respect to distance? I found a solution to the ...
-2
votes
1answer
37 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 ...
-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 ...
1
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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 ...
-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 ...
0
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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
1answer
45 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 ...
0
votes
2answers
144 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 ...
3
votes
2answers
53 views

What are the Kinematics of an Irregular Tripod?

It is a common maxim (at least within the Scouting community) that a triangle is the most stable shape. In practice this means structures should have three legs whenever possible, and have cross-bars ...
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 ...
0
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0answers
102 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 ...
1
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2answers
429 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 ...
1
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2answers
66 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 ...
2
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2answers
268 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 ...
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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 ...
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6answers
286 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 ...
0
votes
1answer
44 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 ...
-1
votes
2answers
111 views

Problem regarding bullet penetration [closed]

Which property remains constant when we say that bullets are penetrating the wall? I mean is the resistive force always constant for a given wall (assumed stationary and immovable) irrespective of the ...
0
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0answers
59 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
77 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 ...
0
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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
vote
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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2answers
63 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 ...
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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 ...
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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, ...
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 ...
-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 ...
1
vote
1answer
104 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
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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 ...
0
votes
2answers
81 views

Derivation of a kinematical equation [duplicate]

My question is, we can calculate distance of free falling objects with the equation of $d = \frac{1}{2}gt^2$ where $d$ is distance in meter, $t$ is time in seconds, but I wonder how we achieved this ...
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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 ...
5
votes
2answers
266 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
115 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
83 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". ...
1
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3answers
329 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?
3
votes
0answers
139 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 ...
-1
votes
1answer
73 views

How is movement possible? [duplicate]

This is a weird question that I wasn't sure where to ask. Say I have two points A and B. I roll a ball from A to B. Between A and B there are an infinite number of points right? Wouldn't it take an ...
-1
votes
2answers
45 views

Proof of a fact involved two cars motion [closed]

Two cars A and B start to move in the same direction. A starts to move with acceleration $5 m/s^2$ and B with $4 m/s^2$. After 15 min A runs with uniform velocity. B continuously runs with ...