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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123 views

Exertion from swinging on a playground swing

I've read about how by tilting one's body one changes one's center of mass while swinging on a playground swing, and thereby increases the energy of the swing. But I would like to get a better sense ...
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4answers
493 views

Calculate average speed with unknown variable accelaration

I am in the middle of a vehicle tracking project where I have to calculate the distance traveled by the vehicle in a given amount of time. Data I am getting: ...
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1answer
90 views

Basic vertical projectile motion

A ball is thrown from the top of a tower with a certain initial speed. It's downward acceleration is g. But why? the initial force makes no difference? and, if not, if I get a revolver and shoot down, ...
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412 views

Angle needed for object A to intercept with object B

Object B is 15 degrees East of North at a distance of 20km/h. Object B is moving at an average speed of 30km/h in the direction 40 degrees East of North. If object A is capable of moving at 100km/h, ...
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1k views

Calculate Mass based on Velocity and Acceleration

I am attempting to design a obstacle avoidance system with the Arduino. My position (for now) is going to be stationary. I will be detecting an incoming object and I want to use the below known ...
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2answers
232 views

Steering forces on a bicycle

Ok, I always notice this weird thing and try to overcome it but cant. Ok as shown in the image when I ride the bike by just one hand and pull the handle back say from the right side so as commonly the ...
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1answer
306 views

1D Motion under Gravity

I have attempted this question in so many different ways but I am getting nowhere. Could someone point me in the correct direction so I can work it out myself? Here is the question: An object $K$ ...
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2answers
378 views

Why can't some light ever reach earth? [duplicate]

Note: I'm a layman in physics. Excuse me if this question is a duplicate, I lack the knowledge in technical terms to find the answer to this by research (I've tried). Let's suppose there's a star ...
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1k views

Relation between the time, velocity and acceleration

This is question from I.E. Iredov's General Physics: $1.22$ : The velocity of a particle moving in the positive direction of the $x-axis$ varies as $v = α \sqrt x$, where $α$ is a positive ...
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2answers
808 views

How can I solve for time without knowing the vertical velocity?

A guy posted this problem on a forum: There is a bird sitting on a pole of height h. you throw a rock at it and the moment the rock leaves your hand the bird starts flying horizontally away from ...
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3answers
531 views

Functions of Time

1) Is position a function of time only or also velocity? Likewise, is velocity a function of time only or also the position? 2) The following are functions of time: $s(t)$ = distance a particle ...
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5k views

Deriving equations of motion using integration

Please refer to my school textbook pg48 (of the book, and not the pdf counter) here: http://ncertbooks.prashanthellina.com/class_11.Physics.PhysicsPartI/ch-3.pdf My doubt is in this context: (right ...
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2answers
1k views

Do you use the magnitude equation to get speed from an accelerometer?

A guy suggested to me that getting speed from an accelerometer required the use of this equation: $\text{speed} = \sqrt{x^2 + y^2 + z^2}$ This does not make any sense to me, all that you would get ...
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1answer
448 views

Projectile motion in two and three dimensions question?

So I bought this book in the library and physics fascinates me and I found this quote in the book " Galileo has proved that when any effects due to air resistance are ignored, the ranges for ...
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2answers
1k views

Calculating force required to stop bungee jumper

Given that: bungee jumper weighs 700N jumps off from a height of 36m needs to stop safely at 32m (4m above ground) unstretched length of bungee cord is 25m Whats the force required to stop the ...
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1answer
520 views

Intercept a moving object

Object A can move at 50km/h, wants to intercept object B (currently $15^{\circ}$, east of north from A) moving at 26km/h, $40^{\circ}$ east of north. What angle should A take to intercept B? AB is ...
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401 views

Projectile Motion

I know the angle at which a projectile is launched, how far it needs to go, and also the maximum height. How can I find the initial velocity needed (disregarding air resistance)? Currently, I am ...
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1answer
164 views

Do observers at different speeds perceive other speeds differently?

I was told that if a plane takes less time to travel from the China to US as opposed to the other direction due to rotation of the earth. I suspect this is incorrect however. From this scenario I ...
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2answers
305 views

Confusion regarding geodesic of thrown ball - curved or Cartesian coordinates?

I'm confused trying to understand what's happening in terms of spacetime geodesics when a ball is thrown and its trajectory plotted, height against time to give a parabola. I read (from more than ...
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230 views

Trains travelling at different speeds towards a station C

Here's the question: Consider two stations A and B located 100 kilometer apart. There is a station C, located between A and B. Now trains from station A and B start moving towards station C at ...
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2answers
88 views

Acceleration: Value Disparity?

If we consider a ball moving at an acceleration of $5ms^{-2}$, over a time of 4 seconds, the distance covered by the ball in the first second is $5m$. In the 2nd second will $5 + 5 = 10m$. In the ...
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2answers
701 views

2d simulation shooting projectiles that inherit the gun's veocity at a moving target while also moving

Overview: I'm working on programming a simulation that requires 'shooting' projectile-type objects at other moving objects. How can I calculate the angle at which to shoot the object to hit? Details: ...
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3answers
11k views

Find radius of curvature, given a velocity vector and acceleration magnitude?

The particle P moves along a space curve. At one instant it has velocity $v = (4i-2j-k)$ $m/s$. The magnitude of the acceleration is 8 $m/s^2$. The angle between the acceleration and the velocity ...
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2answers
649 views

Given a radius and velocity calculate position of an aircraft banking to make a turn in three dimensional space

Suppose an aircraft is moving at a certain fixed altitude above the ground. It follows a path defined by latitude and longitude. Now if we want to define the position of an aircraft at any point in ...
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293 views

Simple kinematics excercise, throwing something upwards [closed]

I am trying to solve this simple excercise: Question You throw a small coin upwards with $4 \frac{m}{s}$ . How much time does it need to reach the height of $0.5 m$ ? Why do we get two results? ...
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3k views

Solving straight-line motion question for time [closed]

I apologise in advance if this question doesn't appeal to the advanced questions being asked in this Physics forum, but I'm a great fan of the Stack Exchange software and would trust the answers ...
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35 views

Average acceleration versus instantaneous acceleration

Does instantaneous acceleration also changes when direction of velocity changes. I know average acceleration does change.
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3answers
65 views

How do these factors affect the free fall of objects?

Take an example of two balls of different masses being dropped from about 250 meters from the ground. How do the following factors affect free fall: Air resistance. Absence of air resistance. ...
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1answer
35 views

Kinematics and dynamics - what pattern do they portray?

The Equations which are derived for kinematics and dynamics are some patterns related to the body in motion. What is the demarcation in the pattern that kinematic equations and dynamic equations ...
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3answers
176 views

How to find stopping distance of a car? [closed]

I am trying to calculate minimum stopping distance of a car once the brakes are applied. I know the velocity at braking instant, i also know the distance from the obstacle. I found out that $$ d = ...
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1answer
53 views

Necessity of the Notion of Work and Kinetic Energy

I've worked through many example problems in my college physics text in the section on kinetic energy and work. I noticed that if the desired quantity is velocity or force, they can be solved entirely ...
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1answer
87 views

Work done: kinetic energy or area under F-ds curve?

Starting from $$F=ma = m \frac{dv}{dt} = m \frac{ds}{dt} \frac{dv}{ds} = m v \frac{dv}{ds}, $$ leads to work done = integral of F.ds = integral of mvdv = change in KE. Suppose a variable force is ...
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1answer
87 views

Prove the relation between relative velocity ,momentum and energy

In Chapter 8 of F.Mandl's book Quantum field theory, during the derivation of the differential cross section, the following relation is used: $$E_1E_2v_{rel}=\sqrt{(p_1p_2)^2-m_1^2m_2^2} \,\, ,$$ ...
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30 views

Computing the Initial Velocity of an orbiting body

I'm working on a simulation program that replicates the movement of planets around a large celestial body (the sun). This is a three dimensional simulation that uses vectors. At present, I'm ...
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1answer
30 views

Minimum power to pull a sheet of paper [closed]

I'm trying to tackle a question in kinematics, but I miss something and don't know what. The question goes like this: Let a homogeneous pole of mass m be connected to ceiling and lean on the ...
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1answer
233 views

Can there be force without motion?

I am confused. Can you have a force or tension without motion? Take for instance two robots with jet packs connected via a cord, each is flying in opposite directions. The tension of the cord is ...
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1answer
50 views

What does it mean by $t=-1$?

if the position vector of a particle is $\hat{r}=\left(4+3t\right)\hat{\imath}+\left(t^3\right)\hat{\jmath}+\left(-5t\right)\hat{k}$, i want to find at what time this particle passes through the point ...
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55 views

Instantaneous velocity is slope of displacement-time curve?

I have a toss-up question that I'm not sure how to answer. Here it is (true or false): The instantaneous velocity at a particular time is the slope of the displacement-time curve at that position. ...
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1answer
65 views

How to find the function of acceleration respect to time while having the function of acceleration with respect to velocity

As everyone know that the integral of acceleration respect to time will give the function of velocity respect to time. However, my question concern the different case when the function of a(t) is not ...
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2answers
253 views

Derivation of the average Velocity formula with constant acceleration (using calculus)

I have been looking at $$ v_{avg} = \frac{v_{i} + v_{f}}{2}, $$ when the acceleration is constant, where $v_i$ is equal to the initial velocity and $v_f$ is equal to the final velocity. How can ...
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1answer
127 views

A question about finding average velocity and average acceleration

I have trouble understanding the following problem's answer: Which of the following relations are true for any arbitrary motion in space? (a) $v_{avg}=\frac{r(t_2)-r(t_1)}{t_2-t_1}$ ...
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1answer
260 views

Forces acting on a double pulley

In a double pulley system, if the mass of the object is 10 kg and the object is accelerating upwards at 2 m/s$^2$, what is the tension in the ropes? I figured the weight of the box is 100N and the ...
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1answer
93 views

Earth moving over the Sun instead of around [closed]

Let's say you are observing the movement of the Sun and Earth from very far away. After year 1, the Earth creates an orbital plane around the Sun. Since the objects in the universe induce forces of ...
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1answer
76 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 ...
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2answers
394 views

Kinematics question - Newton's Law of Motion [closed]

Question: Find the mass M of the hanging block in the following figure which will prevent the smaller block from slipping over the triangular block. All the surfaces are frictionless and the strings ...
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2answers
75 views

What's The Minimum distance?

My Friend gave me a question today. The question was.:: We have a point A. At a distance of $x_0$ from the point. There is a particle$(P_1)$. Also, a particle is present at the point A $(P_2)$.The ...
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3answers
192 views

Why is the constant velocity model used in a projectile motion derivation?

I was re-studying university physics last week, I'm now in the chapter about kinematics in 2 dimensions and specifically the one treating projectile motion. In page 86 of his book (Serway - Physics ...
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876 views

Why do electrons move towards regions of lower potential?

Can someone explain why electrons move from high to low potential regions in quantum mechanics? By the way, what is the very definition of this potential? Moreover, how does this generalize to other ...
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1answer
37 views

When is the speed specified for an object experiencing an exponential force?

So this is the question given in my text book: A particle of mass m is at rest at the origin at time $t = 0$. It is subjected to a force $F (t) = F_0e^{–bt}$ in the $x$ direction. Its speed ...
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1answer
89 views

rectlinear motion with constant acceleration [closed]

Friends, this is a numerical homework problem. I tried my best to solve it but my answer is not matching with the one given at the back of the text book. Please help me out: A motor car moving at a ...