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.

learn more… | top users | synonyms (2)

3
votes
2answers
63 views

Why do tops move opposite to each other when colliding, not tangentially?

When two well-balanced tops collide, they tend to bounce directly away from each, in other words along the line connecting their centers. Intuitively I would expect the tops to move tangentially, not ...
0
votes
0answers
30 views

Relation between linear and rotational motion of molecules?

The temperature of a substance, such as an ideal gas, can be related to the root mean square speed of the molecules. For example, for gases the molecules travel at about 480 meters per second. If we ...
1
vote
2answers
77 views

The force causing galaxies to accelerate away from each other?

The galaxies in the universe appear to be accelerating away from each other according to the Doppler shift that is present in the light we receive from other galaxies. According to Newtonian ...
6
votes
3answers
993 views

Is Torricelli's law “wrong” for big holes? - Tank draining problem

Consider a tank full of water with a constant cross-sectional area A1 placed vertically on the ground. Now someone drills a hole of an area A2 in the bottom of the tank, and the liquid starts escaping ...
-1
votes
1answer
112 views

How Do Low Kinetic Energy and High Kinetic Energy Atoms Attraction differ?

Will atoms of 2 difrent energy levels electron and/or Kinetic attract more than 2 Atoms at he same energy level? Do 2 high energy level atoms attract more than 2 low energy atoms?
0
votes
1answer
112 views

Projectile time of ascent not equal to the time of descent?

Why is the time of ascent less than the time of descent in a projectile motion. I understand that while going up the air resistance and gravity act downwards and while coming down gravity is ...
1
vote
2answers
65 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 ...
1
vote
1answer
537 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 ...
1
vote
1answer
202 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 ...
0
votes
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 ) ] ...
1
vote
1answer
65 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 ...
0
votes
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: ...
0
votes
3answers
247 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 ...
1
vote
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?
1
vote
1answer
72 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?
3
votes
1answer
75k 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 ...
0
votes
1answer
21 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 ...
2
votes
3answers
118 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, ...
0
votes
1answer
30 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 ...
1
vote
4answers
55 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 ?
0
votes
1answer
49 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 ...
0
votes
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 ...
3
votes
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 = ...
1
vote
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?
0
votes
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: | _ _ _ _ _ _ _ _ |/_\ _ /_\___/_\ _ /_\___/_\ _ /_\___/_\ _ /_\___ | \_/ \_/ \_/ \_/ \_/ \_/ ...
1
vote
2answers
46 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 ...
0
votes
1answer
57 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 ...
0
votes
2answers
53 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 ...
0
votes
0answers
34 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, ...
0
votes
2answers
90 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 ...
1
vote
2answers
63 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 ...
1
vote
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 ...
0
votes
4answers
494 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
votes
1answer
44 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= ...
1
vote
1answer
37 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, ...
0
votes
2answers
58 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
votes
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 ...
0
votes
1answer
522 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
votes
2answers
233 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
vote
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
votes
1answer
57 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
vote
2answers
89 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
votes
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
42 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 ...
1
vote
2answers
57 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 ...
1
vote
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
votes
0answers
31 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
votes
11answers
50k 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
votes
5answers
351 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 $\rm K.E.$?
0
votes
2answers
95 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 ...