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votes
1answer
32 views

Can you please explain the statement in the David Morin's Classical Mechanics?

For example, in a hanging massless rope, or in a massless rope hanging over a frictionless pulley, the tension must be the same at all points, because otherwise there would be a net force on at ...
0
votes
3answers
77 views

Why bodies with different masses reach gound at the same time in vacuum? [duplicate]

According to Newton's Gravitation Equation $$F=G \dfrac{M\cdot m}{r^2}$$ force of gravity depends upon mass of both objects, and $$F=ma$$ means force is proportional to acceleration. Then why do ...
0
votes
1answer
44 views

Braking systems on cars

I thought of a maths problem for myself to solve, as it seemed like a good problem to try to get my head around. My issue is that I got stuck at the first hurdle. I was reading up about the braking ...
1
vote
5answers
533 views

Acceleration in circular motion

Can motion of a particle be circular if the radial acceleration is zero, but the tangential acceleration is not $0$?
-1
votes
3answers
59 views

Explanation on Newton's second law

I have asked a question on I pushing the wall,where the force of me is not zero but as per the formula F=m.a,the force is zero and then I got the answer , it is because here the net force is acting ...
1
vote
4answers
95 views

Force = Mass ⋅ Acceleration [duplicate]

I have a doubt on the formula, $$F=m\cdot a$$ In pushing the wall, as per formula, $F= m\cdot 0=0$ as there is no acceleration hence zero. Therefore force become zero. But we have applied some force ...
1
vote
3answers
48 views

Question about a crate in an accelerating truck and friction force

"A crate is sitting in the center of the back of a flatbed truck. As the truck accelerates to the east, the crate moves with it, not sliding on the bed of the truck. In what direction is the friction ...
3
votes
3answers
152 views

How does a particle move under a constant 4-force?

This question pertains specifically to the case of a constant pure 4-force in special relativity, of the form $\textbf{F} = (f_0, f_x, 0, 0)$, where $f_0 = \frac{γ}c \frac{dE}{dt}$. I understand how ...
0
votes
1answer
50 views

What is tension in cabel of elevator? [closed]

A block of mass $m$ is kept on the floor of an elevator of mass $M$ and the system is accelerating upward with acceleration $a$. The acceleration due to gravity is $g$. $F_n$ is Normal force on Block. ...
1
vote
3answers
48 views

The normal force in an elevator that's accelerating

I read a problem about a person is standing on a scale in an elevator. When I read the answer, there was an explanation saying that when the acceleration of the elevator goes upward, the normal force ...
0
votes
0answers
26 views

Finding the acceleration constraint of multiple pulleys

Hello there, I'm trying to understand how Pulleys work. The question asked me to calculate the acceleration constraint that relates the accelerations for each of the masses $m_1, m_2, m_3$. The two ...
1
vote
2answers
41 views

Increasing Mass VS Increasing Force when pushing a Box [closed]

If we assume g=10m/s^2 & negligible friction The force needed to accelerate that box by 5m/s^2 would be 500N. This is a very basic one. The confusion came when an force of 250N (the force a 25kg ...
16
votes
7answers
6k views

Why doesn't the Earth's acceleration towards the Moon accumulate to create noticeable motion of the earth, towards the moon

I get that Earth's mass is very large, so its acceleration is very tiny. But wouldn't the acceleration accumulate over a period of time and become noticeable?
1
vote
0answers
48 views

A query on Newton's second law [duplicate]

Upon studying Newton's second law, I noticed that it seems less of a physical law i.e. outcome of some experiment, than something we built upon how WE define mass and force. The ratio of the masses $...
2
votes
3answers
92 views

What is wrong with this reasoning?

Suppose a particle is rotating about a point at a distance $r$, then since $r$ is constant $\frac{\text dr}{\text dt}=0$ so the component of velocity along the position vector should be zero. ...
0
votes
0answers
16 views

Is there any force that affect to wearable accelerometer underwater?

I am trying to find displacement of underwater sport player with my accelerometer sensor. My question is; is there any force that affect to an object that weared by a human underwater? Thanks.
2
votes
8answers
2k views

What if Force was not Mass times Acceleration? [closed]

We know that Force equals Mass times Acceleration, $F = ma$. But what if we had a law like $$F=m^2a$$ or $$F = 2ma~?$$
3
votes
2answers
85 views

How is normal force in circular motion?

Let's say I have a vertical ring and a bead is sliding on it. I understand normal force is always acting radially and that in general the radial component of weight is not equal to the normal force....
1
vote
2answers
85 views

Force and center of mass acceleration

https://i.stack.imgur.com/3w7Mt.png I have a rod with mass $m$. Above are two ways I can apply a perpendicular force to the rod. Since the mass of the rod is uniform, its center of mass is in the ...
0
votes
1answer
54 views

Does a black hole have thrust? Could they be acting as galactic engines? [closed]

I identify four possible kinds of thrust below (there may be more or less). I don't know how to do the math to test them though. Direct transfer of kinetic energy as thrust. The energy of objects ...
1
vote
3answers
48 views

If you were to push a block in space in an ideal vacuum scenario with zero friction, what would be the final velocity of that object

Say you push an object with 10 N force(just once and let it go) of mass 10kg object in space with zero friction and nothing in the way of its path. What would be the velocity of that object? I would ...
3
votes
2answers
69 views

Acceleration of two bodies on an incline and the normal between them [closed]

Question: What is the acceleration of each body, if they slip along the incline? What is the normal between them? Assume the incline to be frictionless and neglect air resistance. My teacher solved ...
1
vote
1answer
45 views

Convert inertia formula to excel calculator

I've been looking at this question: "Weight" of moving object in a car collision but to be honest I can't get my head around how to work it out myself (I'm not a physics student!). What ...
0
votes
1answer
35 views

maximal acceleration of a wheel-driven vehicle

I was thinking about the maximal acceleration of a bicycle, I found a similar question. What remains unclear is that I found two coefficients of friction, one for rolling and one for static friction. ...
0
votes
1answer
45 views

Force during collision would be very high, would it cause a very big damage? [closed]

So suppose a body of mass 10kg travelling at 5m/s crashes into a wall, the time of deceleration would be very minute, say 0.01 second, then the magnitude of deceleration would be $$\frac {0-5}{0.01} ...
8
votes
3answers
415 views

Regarding Goldstein's claim that $\mathbf{F} = \dot{\mathbf{p}}$

From Goldstein: ... The mechanics of the particle is contained in Newton's second law of motion, which states that there exist frames of reference in which the motion of the particle is described ...
0
votes
2answers
39 views

Acceleration of The Centre of Mass of A Rod

The acceleration a of the center of mass of a system is equal to F/M, where F is the net external force and M is the total mass of all the particles of the system, or at least that is my current ...
2
votes
2answers
84 views

How and why does momentum get transferred? [closed]

Let us imagine an isolated system and there are two objects of whatever masses and size. Let one object move towards the other object with constant velocity. We know, that when they collide, the ...
17
votes
6answers
498 views

Can you jump higher if you run? If so, why? (High jumping)

I have often wondered why high jumpers can jump higher if you run. The way I see it is that you only build up horizontal speed, and since you're running on a plane, I cannot see how this speed can be ...
0
votes
2answers
227 views

Torque, Angular Acceleration and Linear Acceleration

We know that we torque is applied, it cause an angular acceleration in the rotating body similar to what a force does to a body moving on a straight line. But my question is, Does Torque affect the ...
0
votes
1answer
60 views

Does the rope stretch when the pulley of Atwood's machine is accelerated?

Let's say I've an Atwood's machine in which I have two point masses which are different. Now, when I accelerate the pulley, the two masses accelerate at a different rate which can be shown by ...
2
votes
3answers
114 views

Possible paradox relating to acceleration, velocity, and work

I recently encountered a question that made me think of this "paradox": Imagine the following situation: There are two forces: Force 1 and Force 2. They accelerate a mass $m$ from the same initial ...
0
votes
3answers
72 views

How force is equal to the product of mass and instantaneous acceleration?

$$\vec{F}=m\vec{a}$$ Suppose that an object of some mass was constantly accelerating ($\vec{a} \neq 0$) through sometime interval. With no doubt, the object had an instantaneous acceleration at any ...
20
votes
7answers
13k views

Why doesn't the Earth accelerate towards us?

According to Newton's third law of motion that states that every action has an equal and opposite reaction. So, if the Earth exerts a gravitational pull on us (people) then even we should exert a ...
0
votes
5answers
45 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 ...
0
votes
1answer
40 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 ...
1
vote
1answer
47 views

Why do cars with 4 drive wheel accelerate faster, from a physics standpoint? [closed]

I know that an 4WD car beats a 2WD car "off the line," but I do no understand the physics behind it. I know that: $$W_{\text{Wheels}} = W_{\text{Engine}} G\,\text{, where } G \text{ is gearing}$$ $$F ...
49
votes
14answers
20k 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 ...
1
vote
1answer
73 views

Imminent car crash, should I brake? [duplicate]

So I am sitting at traffic lights, stationary, in my car. A drunk driver has crossed over and is about to hit me head on at 40 mph. I only have enough time to do one thing, hit the brakes or leave ...
1
vote
3answers
159 views

Why equation $F = m a$ is not valid in relativistic physics but $F = dp / dt$ is valid?

I read that the equation $$F = m a$$ is not valid in relativistic physics. Instead $$F = \frac{d }{dt} \frac{mv}{ \sqrt{1- \frac{v^2}{c^2} } }$$ is valid in relativistic physics but why is that?
2
votes
1answer
80 views

How does an object in space travelling at constant velocity have a net force of zero acting upon it?

If the definition of balanced forces is "two opposing forces that are equal" and an object with a net force of zero acting upon it means that the forces are balanced on the object, then it should ...
1
vote
1answer
39 views

How is the acceleration proportional to the net force over the mass? [closed]

The acceleration is inversely proportional to the mass when the force is constant. Also, the acceleration is proportional to the force when the mass is constant. So, how can the acceleration be ...
0
votes
1answer
298 views

How would you calculate the force of a hammer hitting an anvil? [duplicate]

If I were to hit an anvil with a hammer (let's say a 1 kg hammer at 1 m/s) how would the force of the impact be calculated? So, where I'm at with this is that I know the deal with f = mv, so the ...
0
votes
1answer
31 views

Particle simulation: understanding mass

I'm trying to understand how mass factors into forces acting on particles in a simulation. For the sake of argument, imagine a 1-dimensional simulation of a particle, whose position is 0 on the x-...
-2
votes
2answers
79 views

Why is force related to acceleration instead of velocity?

I know $F=ma$, but it's never really made sense to me. Here's an example: Hypothetical scenario- I push a bowling ball ($m = 4\,\rm kg$) sitting on the floor with $5\,\rm N$ of force. (Assume no ...
1
vote
2answers
69 views

How is force related to launching objects with a lever?

Suppose we have a class 1 lever, lifting a load of constant mass. All distances remain the same and the only thing that changes is the magnitude of the force applied (effort). Intuitively we know that ...
0
votes
1answer
225 views

What does 'driving force of the engine' mean?

I am given this question: A truck of mass $2000\ \rm kg$ accelerates from $5\ \rm m/s$ to $20\ \rm m/s$ in $5\ \rm s$. Then i am asked to find the driving force of the engine. So, what does driving ...
-1
votes
2answers
102 views

Why Gravity doesn't affect Horizontal acceleration/motion?

It is still hard for me to grasp on why gravity doesn't affect horizontal motion, doesnt gravity causes a change in resultant force and thus cause a change in acceleration $F=m.a$
0
votes
1answer
140 views

Calculate top speed of vehicle [closed]

I'm trying to figure out the top speed of a vehicle and the time it would take to get there. Information about the vehicle: Mass $m = 200 \, \mathrm{kg} ;$ Engine power $= 1000 \, \mathrm{W} ;$ ...
1
vote
1answer
53 views

Acceleration value if coulomb's force equals to 0?

If i have a point in an electric field where the coulmb's force is equal to 0 does this mean that the acceleration and the velocity of the charge q in the mentioned point are also equal to 0? In this ...