All Questions
143 questions
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Elusive force opposing friction between passenger and seat in a decelerating car
A car traveling at 20m/s stops a distance of 50m. Assume deceleration is constant. The coefficient of static friction is 0.5 and coefficient of dynamic friction in 0.03. Will a 70kg passenger slid ...
- 104
1
vote
1
answer
175
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Is dynamics only concerned with systems that are accelerating?
I'd just like to check my understanding of the branches of mechanics. I suspect dynamics is not just concerned with accelerating systems. Doesn't dynamics just generally deal with systems in motion? ...
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4
answers
1k
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Momentum with Constant Acceleration
Can someone correct my understanding on this?
So, if an object has constant acceleration, and travels a distance $x$, it means its momentum will change by $mv_2 - mv_1$.
Now, if the same object ...
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2
answers
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Is direction of velocity and acceleration is same?
We know $\vec F =m\vec a$
Then $m\vec a =\frac {d\vec v}{dt}$
If this equality holds, this means direction of velocity vector and acceleration vector is same.
How this could be possible? What ...
- 303
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2
answers
1k
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Do linear motion equations follow from any of the Newton's three laws?
The distance $x$ covers in time $t$ by a body having initial velocity $u$ having a constant acceleration $a$ is given by $x= ut+(1/2)at^2.$ Does this result follow from any of the Newtonian laws? ...
- 133
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2
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Differentiate b/w scalar and vector in Newtonian mechanics
I am reading the definitions of vector and scalar quantities.
Scalar quantity - quantity with magnitude only.
Vector - quantity with magnitude and direction.
After that we have some quantities to ...
user141345
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2
answers
83
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Can a solid object gain speed instantly?
Is it possible for a solid real world object to instantly gain speed without having to accelerate from $v = 0 \, \text{m/s}$ to $v = 1000\,\text{m/s}$, or does it have to accelerate in order to reach ...
- 193
6
votes
3
answers
2k
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Is acceleration continuous? [duplicate]
The extrapolation of this Phys.SE post.
It's obvious to me that velocity can't be discontinuous, as nothing can have infinite acceleration.
And it seems pretty likely that acceleration can't be ...
- 660
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7
answers
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Can an object *immediately* start moving at a high velocity?
What I mean is, suppose a ball is fired from a cannon. Suppose the ball is moving at 100 m/s in the first second. Would the ball have started from 1m/s to 2m/s and gradually arrived at 100m/s? And is ...
- 389
0
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Centripetal acceleration with vector components
I'm working on solar system simulation and I need to implement centripetal acceleration. The problem is I don't know how it looks like in vector form. I mean I have these formulas:
Velocity
$$ ...
- 11
1
vote
3
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4k
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Does Kinetic Energy assume constant acceleration?
Okay, I've always been someone who doesn't learn anything unless I can prove it. In this case, I set out to prove the Kinetic Energy formula and (wrongly?) found that it was based on constant ...
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-1
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1
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Is there any reason why acceleration should not be the first derivative of the absolute value of velocity? [closed]
I ask mainly because I am not familiar enough with newtonian mechanics and higher-level physics in general to know the repercussions of such a change, but on the simpler plane of existence, I have ...
- 1
3
votes
5
answers
20k
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Radius of centripetal acceleration
Suppose you are moving in circle of radius $r$. So there should be centripetal acceleration towards the center. Now you want to decrease the radius of the circle, so someone should apply more ...
- 53
2
votes
2
answers
698
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Is the magnitude and direction of gravity on an object the same as the objects vertical velocity?
I need to make a diagram for an entry level college physics class. I need to show the magnitude and direction of gravity on a flying object and also show the magnitude and direction of the objects ...
- 21
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2
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2k
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Average acceleration: why I am getting different results?
Let's consider a simple school problem.
A car starts moving during 3 seconds with a constant acceleration of 1 m/s^2.
Then it stops accelerating and moves 3 seconds more with a constant speed.
Find ...
- 31
0
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3
answers
1k
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Acceleration of moving reference frame
I want to simulate the readings of an accelerometer that is arbitrarily moved through 3D space. In an inertial reference frame $W$, the motion of the accelerometer is described by it's linear ...
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2
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1k
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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 ...
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1
answer
66
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Relationship $v_A^2-v_B^2=2a_t\Delta s $ for motion with constant tangential acceleration [closed]
I can not understand a relationship in the general motion in the plane. I am considering a point, which follows a curved trajectory. Indicate A and B two different position of the trajectory and $v_A$ ...
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3
votes
4
answers
2k
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In perfect vacuum (no external force), if I apply a small amount of force to a body, will it continue to accelerate forever?
According to the equation $F = ma$, the greater the force applied to a body, the greater its acceleration. But in a place where there is no gravity or any other kind of external force, if I apply a ...
- 227
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4
answers
5k
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Force required to send ball in set trajectory
If I have a desired 2D trajectory where I know the desired speed of my ball and desired path, and a ball that starts at (x=0,y=0), how can I calculate the required force / point at which the force ...
1
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2
answers
3k
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The acceleration of the centre of mass [closed]
Given two balls that are thrown straight up in the air at a speed of $40 \:\mathrm{m/s}$, $0.10 \:\mathrm{s}$ apart. One ball is twice the mass of the other. The heavier ball is thrown second.
I'm ...
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2
votes
2
answers
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Half-atwood machine with accelerating pulley
This is a follow-up to my previous question, in which I am now trying to calculate the acceleration of the cart (as before, the block surfaces are frictionless). The mass $m_2$ is attached to $M$ via ...
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3
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4k
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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 ...
- 1
0
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3
answers
350
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Condition for 2 bodies to move together
The condition for 2 (or more) bodies to move such that they are always in contact, is that their accelerations (and velocities) along their common normal should be same.
Can someone explain why this ...
- 683
2
votes
6
answers
3k
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Free fall into circular motion
If I'm on a roller coaster free falling from height $h$ and then suddenly start going into horizontal motion with a radius $r$ of turn what is the $g$-force I experience?
I worked out the equation ...
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1
answer
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Calculating time and speed change on downhill incline
I am trying to calculate the time and final speed if lets say a bike with constant speed of 20km/h of goes in this incline (downhill), what would be its speed after say $M$ meter ?
I remember the ...
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1
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2
answers
6k
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If velocity for an interval is zero then is acceleration also zero throughout?
We know that if velocity is zero for an instant, then acceleration need not be zero (a simple example of which is a ball thrown upwards.)
But if velocity is zero for an interval, will acceleration ...
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25
votes
7
answers
12k
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Zero velocity, zero acceleration?
In one dimension, the acceleration of a particle can be written as:
$$a = \frac{dv}{dt} = \frac{dv}{dx} \frac{dx}{dt} = v \frac{dv}{dx}$$
Does this equation imply that if:
$$v = 0$$
Then,
$$\...
- 393
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3
answers
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How to find stopping distance of a car? [closed]
I am trying to calculate the minimum stopping distance of a car once the brakes are applied. I know that $F = ma$, and the braking force is $F = \mu N = \mu m g$, so
$$a = \mu g.$$
Next, by applying ...
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2
answers
330
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How long does it take to optimally change position and velocity?
A spaceship moving in two dimensions is at position $(x, y)$ and has a velocity $(v_x, v_y)$. It also has a maximum acceleration $a_{max}$. Its goal is to be at position $(x', y')$ with a velocity of $...
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3
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1
answer
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Two vehicles moving in a line with different accelerations
Let two similar vehicles starting at rest in a straight line (with a distance of $D$ between them) have time-varying accelerations in the same direction. If both of them have similar time varying ...
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0
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3
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661
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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 ...
- 495
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2
answers
2k
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Non-Constant Acceleration due to Gravity
Recently, I had the first physics lab for my university physics course. This lab was fairly simple, as we were merely using a computer and a distance sensor to graph the position, velocity, and ...
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2
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716
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How to find time, acceleration under this situation
I am trying to solve the following.
An object of mass $m$ slides on a horizontal surface with initial velocity $v_0$. If the kinetic friction between the object and mass is given by $\mu$, find the ...
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4
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3
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Does a heavy body move with the slightest force on a frictionless surface?
If I apply horizontal force on a body resting on the ground, my force will be opposed by the frictional force and the body will accelerate at the point where my force exceeds the force of friction = $\...
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6
answers
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How can an object with zero acceleration move?
My physics text has a problem in which it is said that a person moves a block of wood in such a way so that the block moves at a constant velocity. The block, therefore, is in dynamic equilibrium and ...
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12
votes
3
answers
1k
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Is acceleration an average?
Background
I'm new to physics and math. I stopped studying both of them in high-school, and I wish I hadn't. I'm pursuing study in both topics for personal interest. Today, I'm learning about ...
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2
votes
1
answer
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Kinematics with non constant acceleration
A particle experiences an acceleration described by
$$
a=kx^{-2}
$$
where x is the displacement from the origin and k is an arbitrary constant.
To what value does the velocity v of the particle ...
- 123
1
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0
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One dimensional motion with changing acceleration. Falling to a large body from a great distance [duplicate]
Possible Duplicate:
Radial fall in a Newtonian gravitational field
My math and physics are rusty. I am trying to calculate the time an object takes to fall to a large body. Before you answer $1/...
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2
answers
4k
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Center of gravity of vehicle and vehicle performance
I am interested to know how does CG of vehicle plays role in the Fuel economy and the vehicle performance. Does CG of vehicle has anything to do while accelerating of your vehicle. I am a student, ...
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1
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1
answer
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Calculation of Distance from measured Acceleration vs Time
I have an Accelerometer connected to a device that feeds the instant values of the acceleration in the 3 directions. I've tried to calculate the distance for a vertical movement using these values ...
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3
answers
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How can an object's instantaneous speed be zero and it's instantaneous acceleration be nonzero?
I'm studying for my upcoming physics course and ran across this concept - I'd love an explanation.
- 203
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2
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Using acceleration to plot position
Sorry if this question is dumb, and I know is physics 101, but I'm not that good with physics.
I'm writing an iPhone program that by collecting the acceleration data of the device tries to replicate ...
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