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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-3
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0answers
17 views

about motion in 1D

A body in one dimensional motion has zero speed at an instant. At that instant, it must have: (1)Zero velocity (2)Zero acceleration (3)Non-zero velocity (4)Non-zero acceleration ANS.(1) i want ...
-5
votes
0answers
19 views

Mechanics - motion problem [on hold]

. A particle starting from rest accelerates at 2m/s2 for some time and then travels uniformly and passes a point 175m from the starting point 20m after start. The velocities of the particle at the ...
0
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2answers
51 views

Vertical Circular motion - Tension and velocity

I read through the question Minimum velocity of the particle at the highest point which is quite similar to my questions. But I still have some doubts in the answers - "The particle will complete ...
-2
votes
1answer
18 views

Maximum horizontal speed and vertical speed interdependently [on hold]

I need to limit hspeed and vspeed taking direction in count, I know how to calculate the maximum speed as a whole, but not limiting that speed by setting the hspeed and the vspeed
-3
votes
0answers
36 views

Finding the speed of a car [on hold]

There is one car which got stolen which goes from the point $30$ in the negative sense of the "$x$" axe towards the point $0$ and has a constant speed of $160\text{ km/h}$. Another person notices ...
0
votes
2answers
38 views

A car honking it's horn, how long until the car hears the sound reflected? [on hold]

A car is traveling with a constant speed v on a straight road which forms an angle α with nearby straight wall. When the car is at a distance l from the wall the driver presses the horn briefly. What ...
0
votes
0answers
26 views

Angular Speed and Normal Speed

The instantaneous speed of a point along a circular path is given by $v=\omega r$, where $\omega = \frac{\Delta \theta}{\Delta t}$, $s=\Delta \theta r$, and $v=\frac{s}{t}$. However, isn’t the ...
-1
votes
2answers
37 views

Block over a Block Problem. [on hold]

This a block placed on block problem. In this problem, A block with mass 40 kg in placed on a block of 60kg which lies on a frictionless surface. The coefficient of friction between 40kg mass and 60kg ...
0
votes
0answers
3 views

Water flow in salt solutions contemporary exposed to an electrical and constant magnetic field

When a permanent magnet is held motionless close to a salt solution which already has been exposed to an electrical field a flow in the water will be induced and can be detected by applying some ...
-2
votes
1answer
28 views

Problem: When does a constant velocity catch up to a certain acceleration? What is the maximum acceleration? [on hold]

Physics noob here. Romeo is at x = 0 at t = 0 when he sees Juliet at x = 6m. (a) He begins to run towards her at v = 5m/s. She in turn begins to accelerate towards him at a = −2m/s2 . When ...
5
votes
5answers
99 views

How can we explain the difference in change of kinetic energy, due to different frames of reference?

Imagine a ball ($m= 1\,{\rm kg}$) moving at a velocity $2\,{\rm m}/{\rm s}$ towards a wall. When it hits the wall, it suddenly stops, thereby liberating all its ${\rm KE}$ as heat. Here, the initial ...
-1
votes
1answer
31 views

How can I estimate CO2 emissions for a vehicle travel distance

How can I properly estimate CO2 emissions for a given travel distance (of a private vehicle)? I found the following formula, but I'm not sure that it's correct: ...
0
votes
3answers
64 views

What was the motivation behind the work formula?

Surely there must be a reason we decided to use this as a metric for mechanical energy.How was it developed and what made it more acceptable than other work formula candidates (Like force over time, ...
-1
votes
0answers
38 views

It is possible to have a situiation in which $|\mathrm{d}v/\mathrm{d}t|$ is not zero but $\mathrm{d}|v|/\mathrm{d}t$ is? [on hold]

Please explain the following in detail: It is possible to have a situation in which $\displaystyle\biggl\lvert\frac{\mathrm{d}\vec{v}}{\mathrm{d}t}\biggr\rvert\neq 0$ but ...
0
votes
4answers
99 views

Does a flying bullet get KE from gravity?

A projectile P is shot horizontally at 9.8 m/s from a height of 4.9 m, considering no air friction, after a second it will have v = 9.8 m/s on the x-axis and v = -9.8 on the y-axis. Because of ...
0
votes
1answer
27 views

Minimum turning circle of an accelerating spacecraft

I think I've worked this out, but my maths/physics knowledge is far from perfect, so I'd love confirmation that it is correct. Basically, from $v =\omega r$ and $a_c = v^2 / r$ (where $\omega$ is ...
15
votes
4answers
4k views

Why does the sun make me feel warm?

For a while I thought that the reason I felt warmth from the sun was because my skin was being hit by photons, but then I realized that photons also hit me when I take an X-ray, but I don't feel any ...
-4
votes
0answers
19 views

Kinematics Question: Velocity and Acceleration Polygons [closed]

I think I've been doing too many of these without much rest because I am stumped. The Curved slider mechanism is what is confusing me: Dimensions of a simple 2-bar linkage are given in the attached ...
-3
votes
0answers
15 views

Kinematics-Motion in 1 dimension [closed]

A motor car moving at 20m/s can not come to a stop in less than 3s while for a truck this time interval is 5s. On a highway the car is behind the truck both moving at 20m/s. The truck gives a signal ...
-2
votes
0answers
14 views

Kinematics-Motion in one Dimension [closed]

A man is standing on top of a building 100m high. He throws 2 balls vertically, one at t=0 and the other after a time interval(less than 2s). The later ball is thrown at a velocity of half the first. ...
0
votes
0answers
43 views

Object pursuing exactly toward an uniformly moving object, with a twist

A friend of mine asked me about a problem he faced in an exam, but I happen to be rusty on this and can't seem to even understand it's implications, nevermind solve it. At $t=0$ an object A in ...
-3
votes
0answers
17 views

Controlling the flow of powder from a container, based on grams selected [closed]

was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
3
votes
2answers
148 views

Intepretation of area under velocity-time graph for a bouncing ball

A typical velocity-time graph for a bouncing ball is shown below. I understand that the ball starts from rest at $t=0$, then it accelerates downwards and hits the floor at time $t_1$. Between time ...
0
votes
2answers
33 views

Horizontal and vertical acceleration of a ball on a slope?

I understand that you resolve the components of the balls weight parallel and perpendicular to the slope in order to calculate the force due to gravity that actually acts down the slope. The ...
0
votes
0answers
36 views

River Boat Problem with a Twist [closed]

I am trying to solve the following river boat problem. A river of width $w$ is floating such that the stream velocity varies with $y$ as $$v_R=v_0(1+(\frac{\sqrt 3 - 1}{w})y)$$ where $y$ is ...
1
vote
2answers
61 views

Projectile motion of Golf ball- Can projection height be calculated just from initial velocity and travel time? [closed]

A Golf ball projected with a horizontal velocity of 30 meter per second and takes 4 second to reach the ground. Calculate the height the golf ball was projected from. Calculate the magnitude of ...
2
votes
2answers
56 views

Does deceleration (or negative acceleration) feel like acceleration?

This may seem like a dumb question, but I'm having a hard time trying to intuit the answer. The question is in relation to Einstein's famous thought experiment which says that it is impossible for a ...
2
votes
3answers
168 views

Is there an intuitive explanation of the work formula?

Upon learning calculus, I decided it was time to derive all of classical mechanics to give myself a good understanding of physics. What I found was that, while trying to do so, I would need some ...
0
votes
1answer
45 views

Why do systems with a fixed gear-ratio still use gears?

From my understanding, there are two uses of a gearing system: to change the speed of output rotation (trading it with torque), and to change the axis of rotation. Now, in a car, for example, it is ...
0
votes
4answers
122 views

Why Do Objects move?

Let's imagine a block resting on horizontal table. When We apply a force which is greater than frictional force it moves. But why does this happen? Why can't friction withstand any force? As we know ...
0
votes
3answers
92 views

How can Kinetic energy formula and the Work formula be derived without assuming the other to be true?

After searching how to derive the formula for Kinetic energy, I found that most derivations required the use of the "work" formula. After searching how to derive the work formula for a bit, I found ...
1
vote
4answers
47 views

Car Crash Scenario [closed]

Two vehicles travelling at 80mph in the same direction. Vehicles are directly behind each other. 12 meter distance between them. Front door of car in front rips of and hits the front window of the ...
0
votes
1answer
50 views

When will the velocity of a particle be perpendicular to it's initial velocity?

I am learning kinematics with vector analysis. I was given the position equation:$\mathbf{r} = 10t\hat{\mathtt{i}} + (20t-5t^2)\hat{\mathtt{j}}$. It asks me the time when the velocity of the particle ...
1
vote
2answers
56 views

Kinematics Question AP Physics [closed]

A motorcycle officer hidden at an intersection observes a car driven by an oblivious driver who ignores a stop sign and continues through the intersection at constant speed. The police officer ...
0
votes
1answer
38 views

Can avg. Vel. be zero in uniformly accelerated straight line motion?

A particle moves in a straight line with constant acceleration. The average velocity of this particle in an interval is zero. According to me it may become possible when velocity of particle is in ...
1
vote
1answer
39 views

Nonzero acceleration is compatible with $d|\vec{v}|/dt=0$; why is the reverse not true?

It is possible to have change in magnitude of velocity w.r.t time to be zero and magnitude of acceleration to be non zero, $$\frac{d|\vec{v}|}{dt}=0 \quad \left| \frac{d\vec{v}}{dt} \right| \neq 0\, ...
14
votes
7answers
3k views

Flat throw vs 45 degree throw of a ball

Why does my sports coach tell me that when I'm fielding I should throw the baseball 'flat' to get the maximum distance? I thought from physics that you get the most distance from throwing at a 45 ...
0
votes
2answers
33 views

Distance traveled from displacement

I am currently reading a book called Physics for Scientists and Engineers by Serway. While reading the chapter about 2-dimensional kinematics, I asked myself a ...
0
votes
2answers
83 views

Convert an equation for acceleration into one for velocity

A sledge is pushed in a straight line. Assume surface is smooth. When the sledge is x distance away from the start the magnitude of its acceleration is given by $0.08e^{-4x}$ and is going in the same ...
0
votes
1answer
36 views

rolling a coin or a riding a bicycle [duplicate]

Why somebody riding a bicycle keeps balance and doesn't fall left or right, while is prone to falling when the bicycle stops. One force (to front) shouldn't affect in any way balance left/right. I ...
0
votes
1answer
69 views

Problem conserving 4-momentum at CoM frame in an inelastic collision [closed]

I am confused about the case where mass is not conserved in a collision (not due to relativistic factors). The center of momentum (CoM) frame is not the same before and after the collision. Let's ...
0
votes
2answers
64 views

Energy in the Relativistic COM Frame

I have been taught that in Classical Mechanics, the total energy of a system of two particles in the Centre of Mass Frame is given by $$ E_\mathrm{total} = \frac{1}{2}MV^2 + \frac{1}{2}\mu v_r^2 $$ ...
0
votes
1answer
31 views

the final velocity non-constant acceleration

I'm not sure if my problem was asked before, but if so, a simple link to the answer would be appreciated. Basically I've recently seen videos about spud cannons that use compressed air and it got me ...
0
votes
3answers
89 views

Difference between $|d{\bf r}|$ and $d|{\bf r}|$

What is the difference between $|d{\bf r}|$ and $d|{\bf r}|$ and why are both of them not always equal to each other? My question might seem stupid to some and will probably get downvoted but I have ...
0
votes
1answer
41 views

Explanation about friction force directions of two moving bodies in contact

can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...
0
votes
2answers
72 views

Kinetic friction with no force on an object

We've learnt that friction is the opposition of motion and that friction appears the instant a force is applied on an object i.e when an object is at rest (with no force acting on it) then there is no ...
-1
votes
1answer
39 views

For a projectile to cover maximum vertical distance in the least time, what will be the angle of projection? [closed]

My first guess was 90° as there is no horizontal component for velocity when the angle is 90°. But I could not prove it mathematically (and also I'm not sure if it is really 90°).
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votes
1answer
38 views

Question to find distance at which 2 trains will pass each other [closed]

I was solving some questions related to motion, and I came through a question which I cant understand. The question goes like this: Two trains A and B, 100 km apart are approaching towards each ...
0
votes
2answers
101 views

Is there a situation where $\left|d\vec{v} / dt\right|$ is non-zero while $d|\vec{v}| / dt$ is zero?

Here $\vec{v}$ represents velocity and $dv / dt$ gives the instantaneous acceleration. $|\vec v|$ gives the magnitude of velocity. When acceleration is zero, then change in magnitude of velocity is ...
0
votes
2answers
90 views

Area under v-t and a-t graphs

I know that the magnitude ( i.e. considering all area as positive) of area under v-t graph gives distance travelled by the particle in the given time. But I've been told that magnitude of area under ...