# Tagged Questions

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.

2answers
299 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 ...
1answer
134 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 ...
1answer
114 views

### why does perpendicular motion to the direction of someone' s approach does not affect the distance between them

I was reading about the the four turtles/bugs math puzzle Four bugs are at the four corners of a square of side length D. They start walking at constant speed in an anticlockwise direction at all ...
2answers
123 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 ...
2answers
368 views

### Sign of Velocity for a Falling Object

I'm working on a homework problem in Mathematica. We have to graph the height and the velocity of a function given an initial height and initial velocity. However, when I do the graph for the velocity ...
2answers
74 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 ...
2answers
377 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: ...
3answers
4k 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 ...
2answers
215 views

### Running: Determine how much more energy is needed per extra kilogram of weight

(I recently asked this on maths but was directed here) I have recently become a runner and having a keen interest in kinematics I'm very interested in the maths/physics of my running. Can someone ...
1answer
1k views

### Solving straight-line motion question for time

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 ...
2answers
139 views

### Projectile Motion with Drag

The overall goal is to write a Mathematica program that will compute the launch angle that will yield the greatest range with using [RandomInt] function, but I was having trouble with the physics. In ...
2answers
110 views

### Calculating Average Velocity

I understand that the concept of an average of a data list means finding a certain value 'x', which ensures that the sum of the deviations of the numbers on the left of 'x' and on the right of 'x' ...
2answers
90 views

### Why does gravity assist transfer twice the planet's velocity?

In orbital mechanics and aerospace engineering a gravitational slingshot (also known as gravity assist manoeuver or swing-by) is the use of the relative movement and gravity of a planet or other ...
1answer
173 views

### Monkey and tree - projectile motion

The famous scenario: A hunter is trying to shoot a Monkey hanging from a tree. However, this question doesn't mention the monkey jumping down from the tree or trying to escape. (The hunter uses a ...
1answer
175 views

### Non-commutative property of rotation

Addition of angles are non-commutative in three dimensions. Hence some other angular vector quantities like angular velocity, momentum become non-commutative. What is the physical significance of this ...
1answer
59 views

### Am I making the right assumption about a jump discontinuity in the acceleration?

A train heads from Station A to Station B, 4 km away. If the train begins at rest and ends at rest, and its maximum acceleration is 1.5 m/s^2 and maximum deceleration is -6 m/s^2, what's the least ...
1answer
233 views

### Kinematics - Find theta with Coefficient of Friction?

I recently found a problem that looked like this: A box sits on a horizontal wooden ramp. The coefficient of static friction between the box and the ramp is ...
3answers
80 views

### Estimate quarter mile time

I need to estimate a drag race quarter mile time given the car's weight, bhp and preferably the drive (FWD, RWD, 4WD). I know $v(t) = ds/dt$ and $a(t) = dv/dt = d^2s/dt^2$, but how can I get the ...
2answers
102 views

### Looking for the curve traced by a moving bicycle when its steering bar is fully rotated

I am looking for a curve traced by a moving bicycle when its steering bar is fully rotated either clockwise or anti-clockwise. How to model it mathematically? Is the curve a circle? My attempt is ...
1answer
690 views

### Trajectory of projectile thrown downhill

I'm teaching myself mechanics, and set out to solve a problem determining the optimum angle to throw a projectile when standing on a hill, for maximum range. My answer seems almost plausible, except ...
1answer
627 views

### What's wrong with this equation for harmonic oscillation?

The question: A particle moving along the x axis in simple harmonic motion starts from its equilibrium position, the origin, at t = 0 and moves to the right. The amplitude of its motion is ...
2answers
210 views

### Kinematics Problem

The question asks me to find the angular velocity. Now I do not want you to solve my homework, I want explanation please. It states that the acceleration of point P is \$\vec{a}= -3.02 \vec{i} ...
1answer
1k views

### Ascent rate and size of balloon

I am part of a school project, Project Stratos to send a balloon to the edge of space (the closer side :P) and was wondering how you would work out the accent rate of a large balloon (roughly 1m^3 of ...
2answers
787 views

### Projectiles problem solving

I've only learned about to use kinematics equation when solving projectile problems but today i came across the following equations. where does they come from? Distance travelled Time of flight ...
1answer
103 views

### Utilizing maximum acceleration $a$ for displacement $d$ with initial velocity $v_0$ and final velocity $v_1$

Problem My goal is to move an object from point a to b (displacement $d$) as fast as possible utilizing the maximum available acceleration $a_{max}$, taking into account the initial velocity $v_0$ ...
0answers
70 views

### What is the initial velocity of a projectile so that it passes through a target point in its trajectory? [closed]

Let's say I have a projectile being thrown by a player in my 2-D game. I want to work backwards and find the initial velocity to apply to the projectile such that it passes through a target point in ...
0answers
63 views

### Getting pairs of angle and velocity for a projectile to a given destination

I'm trying to calculate the initial velocity $v_0$ and angle $\theta$ for a given destination $(x, y)$ with a launch height of $y_0$. Obviously there will be a set of pairs of velocity and angle that ...
1answer
68 views

### Shooting a bullet at a system of blocks [closed]

So, I made this question up myself.... and I'm curious about the answer. It requires only secondary-school-level knowledge of physics: You have a surface (ground) with a certain coefficient of ...
0answers
51 views

### I need help with the following Physics' questions [closed]

I need to know which formulas and the step-by-step answers for the following physics questions: 1. You throw a ball upward with an initial speed of 7.0 m/s, and it returns to your hand o.92 ...
0answers
47 views

### A 0.1kg ball of dough is thrown up with a velocity of 15m/s. What is the momentum halfway up? [closed]

I know that $p=mv$ and (0.1kg)(15m/s)=1.5 kg m/s and the momentum at the vertex is 0, but what is the momentum halfway up?
0answers
43 views

### How to calculate the correct coordinates from a distorted video of a projectile?

I am working on a high school project that is related to projectile motion. I am exploring how exactly the position of the center of mass affects the trajectory of a long but thin, javelin-like ...
1answer
132 views

### Projectile motion problem with upward acceleration and horizontal velocity [closed]

An electron in a cathode-ray tube is traveling horizontally at 2.10×10^9 cm/s when deflection plates give it an upward acceleration of 5.30×10^17 cm/s^2 . B.) What is its vertical displacement during ...
0answers
79 views

### Kinematics algebra, pT, Peskin Eq.17.59

my question concerns the kinematics of 2 to 2 particle scattering. I refer to Peskin and Schroeder eq.17.59 going from this expression ...
1answer
606 views

### How to find acceleration given position and velocity?

Sorry for this very simple question but I am still very new to the laws of motion. I am dealing with 2-dimensional vectors in my programming environment and I'm following these slides to learn about ...
0answers
183 views

### How to model an accelerometer measurements on a car wheel?

I am working on kinematically modelling an accelerometer on a car wheel. When working on the initial conditions, I am confused whether or not I should use the gravitational acceleration since there ...
0answers
96 views

### If a car appears in horison and within 2 seconds passes you by, whats the speed it's doing?

While watching the first 4 seconds of driving at 745 km/h is ludicrous from any angle wondered 1)If we knew the curvature of the earth in a "flat" desert, what would be the speed of the car? ...
0answers
157 views

### How to calculate the resulting velocitys and rotation speed after two concave polygons collide in 2d

so I've been searching google for how to do this, but all anyone seems to care about is collision detection =p, and no results come close to teaching me how to calculate 2d elastic collision between ...
0answers
247 views

### Understanding 1D Kinematics and Uniform Acceleration? [closed]

So I was given the following homework problem: You land on an unknown planet somewhere in the universe that clearly has weaker gravity than Earth. To measure g on this planet you do the following ...
0answers
236 views

### Kinematics textbook illustration

I have trouble interpreting this illustration. I see why r (position) and a (acceleration) are the way they are, but what happened to v? Why is it smaller than its coordinates? Is this another error ...
3answers
121 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 ...
2answers
766 views

### Why do far away objects appear to move slowly in comparison to nearby objects?

When we are sitting in a moving train than nearby stationary objects appear to go backwards...in terms of physics we can use the formula velocity of object with respect ...
2answers
487 views

### Calculating Impact Velocity Given Displacement and Acceleration

Assume a car has hit a wall in a right angled collision and the front bumper has been displaced 9 cm. The resulting impact is 25g. Also, it is evident by skid marks that the car braked for 5m with ...
2answers
213 views

### Simple kinematics excercise, throwing something upwards

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? ...
3answers
581 views

### Very basic question: When to use $s=vt$, $s=1/2vt$, $s=at$ and $s=a/t^2$?

Very basic question: When to use $s=vt$, $s=\frac{1}{2}vt$, $s=at$ and $s=\frac{a}{t^2}$? What was the difference between those?
5answers
172 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 ...
2answers
456 views

### What will be the relative speed of the fly? [duplicate]

It has happened many times and i have ignored it everytime. Yesterday it happened again . I was travelling in a train and saw a fly (insect) flying near my seat. Train was running at a speed of ...
2answers
65 views

### Centripetal Force Acceleration

Suppose you want to perform a uniform circular motion . Then a body performing uniform circular motion horizontally needs an acceleration $= \frac{v^2}{r}$ at each point on the circular path with ...
1answer
155 views

### Experiment to measure initial speed of high speed tennis ball?

I want to devise a way to measure the initial speed of a tennis ball fired from a tennis ball cannon, but without using any speed-measuring devices. Just plan distance-measuring and physics formulas. ...
2answers
714 views

### Preventing a block from sliding on a frictionless inclined plane

I want to demonstrate what force $F$ you would have to exert on an inclined plane of angle $t$, mass $M$ to prevent a block on top of it with mass $m$ from sliding up or down the ramp. I worked out ...
3answers
174 views

### If my acceleration is -1 ($a=-1\:\rm{m/s^2}$) and I'm standing in the infinite ($x_0=\infty \:\rm m$), could I reach the point $x=0\:\rm m$?

I'm standing in the infinite where $x_0=\infty \:\rm m$. If I have a negative acceleration, could I reach the point $x=0\:\rm m$? Would it be possible to calculate how long would take to reach the ...
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