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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2answers
64 views

Free falling and bouncing back

My confusion arises with free falling body. For a free falling body the displacement ~ time graph has a kink (at the time when the body hit the ground ). at a kink point, a function is not ...
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1answer
528 views

Is there an optimum length for a swing for a childs mass?

If you want to maximize the maximum velocity a child could go, what would be the optimum height? If you wanted to maximize the efficiency of a child "pumping" their legs to gain velocity, what would ...
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1answer
192 views

How to solve Kinematics: two objects meeting in the air

A water balloon is dropped from the top of a 200m high tower. An alert archer at the base of the tower sees the balloon being dropped, waits for 5s, then shoots an arrow at 40m/s straight up towards ...
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0answers
44 views

About the formula of pendulum simple

for the modulation and the simulation of a pendulum simple , I'm Find this formula : a(t) = a0 * sin ( sqrt(g/l) * t * Pi/2 ) - [ k/(mll) * cos ( sqrt(g/l) * t * Pi/2 ) * t ) ] ...
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1answer
60 views

Simultaneous translation and rotation

I would like to describe the motion of a particle in a rigid body by introducing 6 degrees of freedom which are three translational dofs ($u,v,w$ ) in fixed coordinate system $R_0$($X,Y,Z$) and three ...
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1answer
31 views

Force required to produce a specific motion on a particle [closed]

This exercise comes from the Exercises for the Feynman Lectures, Chapter 15. The full question: 15-6 A particle of rest mass $m_0$ is caused to move along a line such that its position is: ...
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3answers
245 views

Animating an Acceleration Vector - Acceleration of object on a crested path in gravitational field

So I was reading in Chapter 3 of my textbook, Sears & Zemanksky's University Physics with Modern Physics by Young and Freedman, 13th Edition, and the discussion took us to a definition of the ...
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0answers
16 views

Projectile motion. Scattered trig ratios, unable to condense [closed]

I have this question from university to complete: A rugby player kicks a ball from the ground aiming to get the ball over the horizontal bar and between the vertical posts. The ball is 50 meters away ...
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0answers
6 views

Average velocity formulas [duplicate]

Total distance/time taken and (Vi+Vf)/2 are both refered to as formulas for average velocity. What is the difference and similarity between these two?
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1answer
65 views

How does friction affect the motion of a pendulum?

I would like to know what is the difference in the equation of motion of a pendulum in the presence or the absence of frictional forces. And how this translates to the solution of those equations?
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1answer
74k views

Solving for initial velocity required to launch a projectile to a given destination at a different height

I need to calculate the initial velocity required to launch a projectile at a given angle from point A to point B. The only force acting on the projectile after launch will be gravity – zero air ...
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1answer
19 views

Do you use static or kinetic friction when calculating this problem?

You are given mass and initial velocity of a vehicle and told that you need to stop. You are given kinetic and static friction and asked to find the minimum distance. Would you use kinetic friction or ...
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3answers
116 views

Can there be motion without the flowing of time? [closed]

tldr - Can we reject the notion of the passage of time, but still accept that motion is real? This question is a follow up to comments between myself and the author of this answer to the question, ...
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1answer
29 views

question from the idea of relative acceleration [closed]

the accelerations of a particle as seen from two frames $S_1$ and $S_2$ have equal magnitude $4 m/s^2$ so my teacher said that the acceleration of $S_2$ with respect to $S_1$ may be anything between ...
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4answers
50 views

For a particle moving in a straight line

If the velocity is zero for a time interval, is the acceleration zero at any instant within the time interval ?
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1answer
43 views

Energy and Momentum: Impact

Boat A has just lost another race to Boat B. In a fit of rage, the driver of Boat A (mass = 500 kg) turns his boat towards Boat B (mass = 450 kg) which is at rest as the driver gloats over yet ...
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2answers
45 views

Regarding Basic laws of motion

When a constant force is applied on body which is free to slide on a surface, does it move with a constant velocity after some time or does the velocity keep on increasing? Please explain it for both ...
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2answers
22 views

Why do the following two constant acceleration equations produce contradicting outputs?

Let acceleration = -a. I'm was originally trying to find the stopping distance in terms of $v_0$ and $a$ Two relevant equations of linear motion with constant acceleration then become $x = ...
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0answers
29 views

Direction of motion 1 [closed]

A man on a bike travelling east on straight road at 8km/h sees a car driving north at 60km/h. What is the apparent speed and diretion of motion of car to the cyclist?
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1answer
39 views

What will happen if you move a photon move in a straight line with no oscillations? [closed]

As light is a wave, it travels in an oscillating pattern: | _ _ _ _ _ _ _ _ |/_\ _ /_\___/_\ _ /_\___/_\ _ /_\___/_\ _ /_\___ | \_/ \_/ \_/ \_/ \_/ \_/ ...
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2answers
45 views

Impulse Equations

A solid sphere of mass $m$ rolls without slipping on a horizontal surface and collides with a vertical wall, elastically. The coefficient of friction between the sphere and wall is $\mu$. After the ...
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1answer
52 views

Impact Speed of a car

A car (Mass 4500 Kg) hits a concrete Block (1000 Kg) on left edge. After impact, block rotates in circular motion and stops at about 24 feet from its initial position. How to calculate force with ...
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2answers
46 views

Free Fall Motion in Physics [closed]

A man in a close elevator with no floor indicator,does not know whether the elevator is stationary, moving upward or moving downward at a constant velocity. To try to find out, the person drops a coin ...
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0answers
32 views

Velocity of an object rolling down a spiral

Imagine a fiction less spring-like spiral, an object will roll down the wire path the spring creates. From conservation of energy, the initial PE will be equivalent to gravitational potential energy, ...
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2answers
85 views

Maximize time of flight and range at the same time in projectile motion

Given the equations of projectile motion (no air resistance), it is easy to find the launching angle theta that produces the maximum range. That angle is 45 degrees. The maximum time of flight is ...
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2answers
59 views

Would this be correct for kinetic energy in special relativity?

In galilean relativity $$p=mv$$ and $$KE=\frac{1}{2}mv^2$$ If I understand it in special relativity the equation for momentum is $$p=\frac{mv}{\sqrt{1-\frac{v^2}{c^2}}}$$ In galilean relativity ...
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1answer
47 views

Vector Navigation and equations [closed]

So I am taking a grade 12 physics online course and I am getting stuck on the Vector Navigation equations as there isn't much explanation in my course. The following text is found in my online ...
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4answers
481 views

Why do I get inconsistent answers with the kinematics equations?

The initial velocity is 14 m/s the final velocity is 0. The distance is 9.0 m and the time is 1.5 s. When solving for the acceleration, why do I get different values when using different kinematic ...
2
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1answer
43 views

Why are my answers wrong for braking distances? [closed]

I have been working on a presentation to find the braking distances at the velocities of cars obeying speed limits for a range of common speed limits. I'm working with the equation $$d= ...
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votes
1answer
38 views

Acceleration problem [closed]

Setting a record in 2009 in a 100-m race, Usain Bolt crosses the finish line taking 9.60 s. Accelerating uniformly from rest, Usain took 1.80 s to attain maximum speed, which he maintained for the ...
1
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1answer
35 views

Projectiles ability to do work to a box when connected by string? [closed]

I was wondering, the work-energy theorem states that KE can do work, as it is Mechanical energy. if the KE energy and thus Mechanical energy of a ball, if external...can do work on an object, ...
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2answers
53 views

One dimensional motion - Why does a ball fall back in my hands when I throw it up in a moving bus? [duplicate]

Suppose you are moving in a bus and you throw a ball upwards. Why does it always land in your hand and does not fall behind you? The bus is moving with a uniform velocity in a straight direction. Now ...
0
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2answers
42 views

Projectile motion problem, insufficient known variables [closed]

I have a physics problem related to projectile motion, I am having difficulties figuring out how to find the initial speed in the $x$ and $y$ directions, as well of the height of the drop. I've tried ...
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1answer
467 views

Relativistic Kinematics - 2-Body Particle Decay

Consider the scenario where a particle of mass $M$ decays into two lighter particles of mass $m_1$ and $m_2$. In the center of mass frame (i.e. $\mathbf{p}_1$ and $\mathbf{p}_2$, the momenta of the ...
2
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2answers
224 views

Time reversal in simple *solution* to equation of motion

Consider the solution to the equation of motion for a particle with a constant acceleration: $$ x(t) = x_0 + v_0t + \frac{1}{2}at^2.$$ If I let $t \rightarrow -t$, then the equation becomes: $$ x(-t) ...
1
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1answer
29 views

Average Velocity? [closed]

May any one explain to me this problem.. A particle moves a distance x_1=20m to the east (+ve direction) in a time t_1=10s. And again to the east a distance x_2=40m in time t_2=20s. Find its average ...
-1
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1answer
55 views

Displacement on a turn with constant speed with a pitfall

A car is driving North-West on a highway. It has a speed of $20 $ m/s with the cruise control on. Ten seconds later, the car is heading North-East (still going $20 $ m/s). Determine the ...
1
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2answers
67 views

In a Distance-Time^2 graph, does the Slope represent Acceleration, or Acceleration*2?

In this graph that I made below, the x-axis is t^2 (time squared), and the y-axis is d (distance). From these axes you can tell that it is a graph showing acceleration. The slope of this line is ...
0
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0answers
16 views

How does the football curve after the direct free kick? [duplicate]

You might have seen that in football, if a player is awarded a Direct Free kick just outside the penalty box and he kicks it, sometimes the ball does not go in a straight line rather it curves in the ...
4
votes
2answers
38 views

Finding the Force of two objects - by using Acceleration but only ONE of the given masses?

I came across the following question in my physics textbook and wanted to try to solve it: A 1700 kg car is towing a larger vehicle with mass 2400 kg. The two vehicles accelerate uniformly from a ...
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2answers
56 views

Trouble with rotational kinematics

I'm having a bit of trouble with the following homework problem: My thinking is there are only three forces acting on the laundry: the force due to centripetal acceleration, the force due to ...
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3answers
8k views

Calculating car's acceleration from change in angle of hanging object?

The question essentially is based on a situation like this- A car has a small object hung from the cieling on a string (apparently at an angle of 0 degrees to the ceiling). The car is accelerating ...
0
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0answers
29 views

What is the derivative of the length vector in the direction of the original unit vector?

What is the derivative of the length vector? I am asking this question becuase I have seen, in Prof. M. S. Sivakumar's youtube video, the result that $\dot{|r|} \hat{r} = \dot{r}$ Where, $ ...
11
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11answers
49k views

How can momentum but not energy be conserved in an inelastic collision?

In inelastic collisions, kinetic energy changes, so the velocities of the objects also change. So how is momentum conserved in inelastic collisions?
4
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5answers
309 views

Does an object move because it has Kinetic Energy or does it have Kinetic Energy because it is moving?

Maybe to explain I'm wondering if an object gains $\rm K.E.$ which causes it to have a velocity or does an object have a velocity which cause it to get $\rm K.E.$?
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2answers
72 views

What is total acceleration?

I'm currently taking a Physics class and we are studying motion in a circular path. and i'm kind of fuzzy on what the total acceleration actually is. take this problem for example An automobile ...
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1answer
45 views

Why can you lift more weight with bad form?

Sorry for the lack of academia behind the subject of the question, however I'm trying to prove a friend wrong. He says that bad form with a deadlift will not allow you do more weight and he's doing ...
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0answers
22 views

Find the maximum height, distance from the launching point and the time in which a rocket has been flying? [closed]

A rocket is thrown at an angle of $53$ $degrees$ with the surface of Earth, with initial velocity $100 m/s$ and initial acceleration 30 $m/s^2$. The engine works only for $3$ seconds then rocket acts ...
0
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2answers
40 views

Using constant snap, what acceleration is required to achieve a desired change in position, with acceleration and velocity bounded

Also assuming you must approach the bounds of acceleration and velocity smoothly -- i.e. their derivatives approach zero as you reach the bounding value. In some cases, you may not reach the bounds ...
0
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1answer
37 views

Kinematics contradicting conservation of energy?

I was having some conceptual difficulty reconciling my intuitive understanding of kinematics with conservation of energy, so I made up a short problem that tested my intuitions: Suppose I define an ...