All Questions
143 questions
4
votes
2
answers
312
views
Force and Accleration
It's just a basic question I had when I was studying physics years back,
So acceleration have two equations
$$a=\frac{F}{m}$$
and
$$a=\frac{\text{d}v}{\text{d}t}$$
So by the first equation, if I'm ...
- 171
0
votes
7
answers
404
views
Vertical motion of an object
We define acceleration as $-9.8\frac{m}{s^2}$ for an object that is thrown upwards due to gravity. My question is when the object reaches maximum height at the point where it is about to turn around ...
- 23
1
vote
2
answers
850
views
Force creates the motion or Motion creates the force?
Motion Creates Force ?:
When you move your hand (to push a box for example), it creates a force.
When electron moves through a wire it creates electrical force.
Or Force Creates Motion ?:
Gravity ...
- 113
3
votes
1
answer
137
views
Average Velocity ($\vec{\bar{v}}$) Intuition and Analogy for Non-Uniform Acceleration
Background
So I was trying to make as much sense out of kinematics through intuition after having taken my first semester of university physics, and I've stumbled onto a dillema that I can't seem to ...
- 66
5
votes
3
answers
2k
views
Does tangential acceleration change with radius? [closed]
Do tangential velocity and tangential acceleration change with radius (change of radius on the same object)?
For example consider a spinning disk. Does the equation $$a_t = \alpha R$$ (where $a_t$ ...
- 87
5
votes
2
answers
476
views
Alternative expression of acceleration in vector form
Let's imagine a one dimensional case, where a particle is moving with a velocity $v$ and an acceleration $a$. Thus
$$a=\frac{\mathrm dv}{\mathrm dt}\tag{1}$$
Applying the chain rule, equation $(1)$ ...
user258881
0
votes
2
answers
3k
views
Why is there no tangential acceleration in uniform circular motion? [duplicate]
I need to know what all is remains constant in uniform circular motion. The tangential SPEED, angular velocity and centripetal acceleration right? Why is there no tangential acceleration in uniform ...
- 87
0
votes
1
answer
109
views
Why is the acceleration of the boulder and pallet half that of the truck [closed]
While working on some homework I accidentally seem to have reached a bit of a mental block on this relatively simple problem.
A 5000-lb truck is used to lift a 1000-lb boulder sitting on a 200-lb ...
1
vote
4
answers
58
views
Can we calculate centripetal acceleration by using this method $\frac{\mathbf v_2-\mathbf v_1}{T}$?
If we know the angle between two velocity vectors $\mathbf v_1$ and $\mathbf v_2$, and if we know the time $T$ it takes for the velocity to change from $\mathbf v_1$ to $\mathbf v_2$,then is it ...
- 315
1
vote
1
answer
103
views
Acceleration vs. time from acceleration vs. distance [closed]
Let's say we have two point bodies, each of mass of 1 unit, 1 unit apart. If we exclude any external forces, gravity starts slowly pulling them towards each other. At some point, the bodies are ...
- 11
1
vote
1
answer
76
views
Determining acceleration in order to meet a space-time-velocity reservation
An Example
A train on a single line track is told to be at position $x_{res}$, at time $t_{res}$, and to be moving at exactly $v_{res}$ when it hits that point. Where $_{res}$ denotes the reservation....
- 11
2
votes
4
answers
2k
views
Direction of average acceleration in circular motion
I know that the instantaneous acceleration is always directed towards the center of the circle.But what about average acceleration.
In the above figure my book says place change in velocity along the ...
0
votes
2
answers
5k
views
Why is Speed of an object equal to square root of distance traveled multiplied square root of acceleration?
I wanted to find the relationship of the speed of a falling object in a vacuum at g=9.8 m/s2 compared to its distance. I wanted to get time out of the equation. When I plotted the relationship it ...
- 247
-3
votes
1
answer
62
views
When to use what centripetal acceleration? [closed]
There are two equations for it: $a_c = v^2 / r$ and $a_c = \omega^2 / r$.
It seems like they give me different values. I don't know when to use which. Can you explain?
- 9
1
vote
2
answers
101
views
Conceptual freshman year physics question about acceleration
A particle moves along the x-axis.
When its acceleration is positive,
A. its velocity must be positive
B. it must be speeding up
C. it must be slowing down
D. its velocity must be negative
E. none of ...
- 11
0
votes
1
answer
2k
views
What does the area under an acceleration-displacement curve represent?
Considering the equation where,
$$
\frac {1}{2} \left (v^2_f - v^2_i \right) = \int_0^s ads\,
$$
What does the left-hand side of the equation actually represent? Is there an intuitive explanation ...
- 5
1
vote
2
answers
131
views
Is the car braking time formula $ T = v / (\mu_s \, g) $ valid only for uniformly accelerated motion?
I'm wondering if the car braking time formula is valid only for uniformly accelerated motion.
$$ T = \frac{v} {\mu_s \, g} $$
with $ v $ average speed, $ \mu_s $ static friction coefficient between ...
- 297
0
votes
3
answers
1k
views
What is going on at point A of this velocity-time graph of a bouncing ball?
I was wondering what the ball is doing physically at point A -- is it as soon as the ball hits the floor? If so, what about the section of the graph after point A? Is the ball just coming to a rest?
1
vote
4
answers
7k
views
Acceleration-time graph for a falling object
I understand that when drawing an acceleration-time graph for a falling object (with initial velocity = 0), the y-intercept should be $9.81ms^{-2}$ and acceleration should end up being $0ms^{-2}$ as ...
- 117
0
votes
1
answer
209
views
Distance traveled by a particle in $n^{th}$ second
My book states that the distance traveled by a particle thrown upward in the last second is independent of it's initial velocity because the the object travels the same distance as a freely falling ...
user238497
1
vote
1
answer
1k
views
Direction of acceleration vector at the apex of a curve
(Test Your Understanding of Section 3.2)
The question wants me to choose the correct acceleration vector, from the given 9 options where 9th option is zero acceleration.
Ok, first I thought option ...
- 876
0
votes
1
answer
404
views
What causes tangential acceleration
The body moves on a circular path and has both tangential as well as centripetal acceleration.
Friction acts outward as shown in figure. If this friction exceeds mv²/r, then shouldn't the body just ...
- 163
3
votes
3
answers
1k
views
Is the acceleration of car greater when hitting the accelerator, or the brakes? [closed]
Is acceleration of car greater than when pedal the pushed to the floor or when break pedal is pushed hard? I do understand that the signs would change in either but I am more considered about the ...
- 41
0
votes
0
answers
385
views
Why don't we define time derivative of acceleration? [duplicate]
When we started the study of kinematics we defined position and its change with respect to time. After that we defined time derivative of velocity which gave us acceleration.
These 3 concepts really ...
- 3,395
0
votes
2
answers
643
views
If an object in free-fall is moving upward, the object's velocity is decreasing. Does this mean that the acceleration is -9.8 m/s/s?
I have a problem (that I am not asking you to solve) where it takes $4s$ for an object to travel upward to its maximum height, and we have to determine how far the object travelled. If the ...
- 129
1
vote
2
answers
3k
views
Find the time when tangential acceleration is equal to radial acceleration [closed]
A particle begins to move along a circular path of radius R with a constant magnitude tangential acceleration of $a_t$. After time $t$ it's the centripetal acceleration is equal in magnitude to ...
- 132
1
vote
2
answers
1k
views
How does centripetal acceleration have direction/vector and magnitude while in the formula $v^2=v\cdot v$ is scalar?
$$a_c=v^2/r$$
1. How does centripetal acceleration have direction or vector while in the formula dot product between velocity vector is scalar (as in kinetic energy)? Radius is scalar quantity. What ...
- 350
0
votes
2
answers
258
views
Intuition for formula of tangential component of acceleration in general curvillinear motion
In certain problems of plane motion, the position of the particle P is
defined by its polar coordinates $r$ and $\theta$. It is then convenient to resolve the velocity and acceleration of the particle ...
- 551
0
votes
1
answer
202
views
When a body completes one revolution around a circular path will its acceleration be 0?
When a body is moving in a circular motion the acceleration keeps changing, will it be zero when it comes back to the same point it started from(will the average acceleration be 0?)
- 1
1
vote
9
answers
12k
views
Why is acceleration variable in uniform circular motion?
Acceleration is the rate of change of velocity. In the uniform circular motion the acceleration is produced due to change of direction of the velocity(the magnitude remains same). The direction is ...
- 127
0
votes
1
answer
59
views
Acceleration formula derivation (newtonian physics) [closed]
Acceleration has a simple equation in physics:
$$a = \frac{(v-u)}{t}$$
(should be $\Delta v / \Delta t$)
Both $v$ and $u$ have $s/t$ as their formula. So, dividing twice by time gives time squared, ...
- 101
0
votes
2
answers
15k
views
The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than [closed]
The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than 250 m/s². If you are in an auto- mobile accident with an initial speed of 105 ...
0
votes
5
answers
733
views
Why do objects move back after collision?
When a ball collides with a wall, the ball moves in the opposite direction, why does this happen if Newton's third law operates. I mean the ball collided with the wall and imparted a force on it and ...
- 117
0
votes
1
answer
180
views
Acceleration in $x$ and $y$ directions of a pendulum swinging? [closed]
If there is a pendulum that gets released and only moves in two dimensions, what would it’s acceleration be in the x and y directions, meaning at what rate is the velocity changing in the x and y ...
50
votes
13
answers
24k
views
Why doesn't a braking car move backwards?
The net force on an object is equal to the mass times the acceleration, $F = ma$
When I brake on a (moving) car, the net force is negative, therefore causing the resulting acceleration to also be ...
- 637
0
votes
1
answer
53
views
Interpreting derivatives
So we have a function such that the distance moved by a particle (say $s$) is proportional to $sin(Ct)$ where $C$ is a constant.
Now i needed to show that the rate of change of velocity is directly ...
- 42
0
votes
1
answer
145
views
Physical meaning of average acceleration
What is the physical meaning of average acceleration?
For example, average velocity is that uniform velocity with which if an object is made to move, it will cover the same displacement in a given ...
- 876
0
votes
1
answer
1k
views
Collision Speed at which seatbelts become ineffective [closed]
In a car, what is the speed at which if you were to crash (eyeballs-out) your deceleration would be so high that your seat belt becomes ineffective and that you would've die whether or not you ...
- 103
-1
votes
1
answer
3k
views
How to find Net Force with constant velocity? [closed]
Does having a constant velocity always make the acceleration equal zero?
For example: A 5 kg ball is moving at constant velocity of 15 m/s. What is the net force on the ball?
If the formula is $F_{...
0
votes
0
answers
76
views
How do you change the acceleration of a tennis ball, connected to a string in circular motion?
I'm a freshman in high school. In Physics we have a question in our lab that I would like to have help on. In the lab, we have a flying pig (or tennis ball) tied up to a string that's connected to the ...
- 9
0
votes
1
answer
197
views
Define when is makes more sense to turn or brake
I try to find a solution for this Problem:
We should compare circular motion with uniform acceleration.
The Task is to find out whether it is better to make a turn if you face a wall in front of ...
- 9
0
votes
2
answers
137
views
Inferring vehicle weight/load
Is it possible to calculate or infer a vehicles weight or relative load
? Ideally I am looking for an indicator that says the vehicle is "empty" or "carrying weight" in terms of its carrying load. ...
- 101
1
vote
2
answers
358
views
Is there such a thing as maximal deceleration/negative g-force?
I was thinking, is there such a thing as negative $g$-force? What if a person is decelerating really quickly? Does that have the same effect as when a person accelerates really quickly? Are the $g$-...
- 147
-1
votes
1
answer
248
views
Why is the speed of a rolling ball related to the incline?
Considering that the gravitational acceleration is constant and the air resistance is insignificant at low speeds, why is it that a ball rolls faster down a steeper incline?
- 11
-1
votes
3
answers
102
views
Accelerating at $\rm 1,000,000 \, m/s^2$ to $\rm 1 \, m/s$?
What would it look like if someone was accelerated at $\rm 1,000,000 \, m/s^2$ to $\rm 1 \, m/s$? Would they die? Would their body stay intact? My guess is that the answer might be more interesting if ...
- 17
0
votes
2
answers
678
views
Calculating friction on a rigid body with multiple friction points [closed]
I am working on a physics simulator of rigid bodies. I am currently struggling with calculating friction of a rigid body with multiple friction points. The simulator is 2 dimensional and from top down ...
- 13
0
votes
3
answers
2k
views
Does a ball, when thrown into the air, ever experience an instant of rest? [duplicate]
Say I walk outside and throw a ball into the air. Obviously it will decelerate as it travels upward due to Earth's gravity, and accelerate as it travels downward for the same reason. But is the ball ...
- 163
2
votes
6
answers
3k
views
Formula to determine acceleration based on constant energy input
I'm a software engineer building a simulator for train movement. What I would like to do is create an acceleration curve that's closer to reality.
This is my thinking, which includes some ...
- 31
0
votes
1
answer
1k
views
How can be Acceleration without force
Newton's first law says that everything will continue it's sate unless compelled by any external force. In my book it is written that "An object will continue accelerating until the resultant force on ...
- 253
2
votes
2
answers
5k
views
How is normal force generated on wedge?
suppose we have a wedge a block kept over it as shown and consider all surfaces to be smooth:
Now block $M$ and $m$ will exert normal ($N$) on each other with same magnitude.
As only force exerted ...
- 253