# Tagged Questions

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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### What is the best way to calculate impact time with collisions?

I've been teaching myself physics and I've been wondering about the impact time in collision calculations. The scenario I've been using to learn is an object with a mass of 4000 kilograms colliding ...
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### Inverted pendulum with reaction wheel

I'm a little confused about the equations of motion of the reaction wheel pendulum. It is used in self balancing bicycles - see vide link in comments (I can't add another link here due to low rep). Or ...
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### Relationship between velocity and position due to constant jerk proof check [closed]

In constant accelaration and linear (1D) motion, we can show that relationship between velocity and position is quadratic (parabola) by We can write $v$ in the form of $v=v(x(t))$ a=\...
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### Angle required to hit the target in projectile motion

Consider the problem of projectile motion where the angle to hit a target $(x,y)$ is asked, once given the initial velocity magnitude $v_0$. The projectile is fired from the point $(0,0)$. Here is ...
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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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### How do you know when to use kinematic equations as apposed to $v = d/t$ and $a = v/t$? [closed]

How do I know when to use v = d/t and a = v/t or d=vi+​1/2​​at^2 and vf = vi + at?​
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### How to determine the net velocity change applied by a force vector [closed]

I am a little stumped by the answer of this question. The question reads, "In three situations, a single force acts on a moving particle. Here are the velocities (at that instant) and the forces: ...
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### Why can't I use conservation of energy to find ratio of final velocities on different planets?

The question is An object of mass $m$ is allowed to slide down a frictionless ramp of angle $\theta$, and its speed at the bottom is recorded as v. If this same process was followed on a planet ...
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### Helicity of massive particle at high enengy

We know that massless spin-1 particle like photon only has two helicity state (-1,1), what about the helicity of massive spin-1 particle (W boson) at very high energy? Does it have helicity 0 state ...
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### Finding acceleration due to gravity of a 2D projectile

Can I find acceleration due to gravity of a 2D projectile given only the peak of the projectile, the point of impact, initial angle, and initial velocity? Specifically what is missing is the initial ...
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### Does the position-time graph have to be a smooth function?

If at some time $t$ there were a discontinuity in the velocity-time graph, then the acceleration would be infinite at $t$. So intuitively, it seems that the velocity-time graph must be continuous. I ...
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### Olympiad problem - struggling with polar coordinates [closed]

This is a physics olympiad problem; and I am still struggling with it. I will quote it here: " A particle moves along a horizontal track following the trajectory $r=r_{0}e^{-k\theta}$, where $\theta$ ...
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### Kinetic energy vs Kinetic Energy scenario in a collision, mechanical energy used for work?

Most collisions have Kinetic energy conserved or in the case of inelastic collisions energy is lost into other forms. Though the equation of "TMEi + Wnc =TMEf" is true however, what if two unequal ...
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### Why do I get two different answers? Using Calculus and Using Newton for Distance/Velocity [closed]

Why do I get two different answers? QUESTION: How long does it take to slow down from 8000 m/s to 6000 m/s with an acceleration of -400 m/s^2 ? GIVENS D distance V velocity T time V initial ...
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### Why the similarity in the Equations of Motion for Rotational and Rectilinear Motion?

These are the equations of motion given constant acceleration, for first rectilinear and then rotational motion. Rectilinear Motion: Rotational Motion: While the variables have changed, and the ...
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### Homework: Expression for minimum speed to cause collision of objects / simple kinematics

I have a question which is worded as follows: Person A throws a rock at a 45∘ angle to the horizontal, aiming at Person B who's standing on a building at heigh h above level ground. At the ...
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### What kind of unit is $m^2s^{-4}$ in terms of gyro/accel?

Background While working on something in the field of avionics, I have discovered the following unit as part of an inertial-physics equation... $$m^2s^{-4}$$ I am trying to figure out the formal ...
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### How can I find the maximum height if I have changing acceleration?

I'd like to find the maximum height that a projectile reaches in motion if I have a non-constant acceleration. How would I do this? What variables do I need to know in order to calculate this? ...
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### Instantaneous Velocity after bouncing off a wall

I have a ball, and I throw it at a wall as a projectile (assume that the ball's position the instant the journey begins is on level-ground). The ball hits the wall with a velocity that is at right ...
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### What decides distribution of momenta and energy in rigid collisions?

I recall in Highschool physics receiving a problem of the form "assume 2 spherical bodies" $P_1, P_2$ enter a collision where $P_1$ has momentum $m_1 V_1$ and $P_2$ has momentum $m_2 V_2$, both ...
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### Explicit Function for Bouncing Ball [closed]

I was wondering if it's possible (and if so, how would you go about it) to write an explicit function for the position of a ball bouncing as a function of time (assuming a coefficient of restitution 0 ...
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### Kinematics:homework question [duplicate]

Q.)A particle goes along a quadrant AB of a circle of radius 5cm with a constant speed of 2.5cm/s as shown.Find the average velocity. Attempt at the solution: 1.I calculated the displacement between ...
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### Why the two different methods yield different answer in kinematics [duplicate]

Q.)A particle goes along a quadrant AB of a circle of radius 5cm with a constant speed of 2.5cm/s as shown.Find the average velocity. Attempt at the solution: 1.I calculated the displacement between ...
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### Kinematics - Non constant acceleration [closed]

A biker traveling the road is 100 km away from his destination, at t=0 (initial time). His speed, at the start point, is 100km/hour, and varies equalys to his distance from the final destination, ...
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### How to find out radius of curvature by knowing velocity and angle with horizontal of a body [closed]

A particle moving in air with initial velocity 100 m/s making an angle 60 degree with horizontal then how to calculate radius of curvature at time equals to one second ??
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### Circular motion and car tire angle [closed]

I'm trying to figure out what angle to turn the front tires of my small robotic car (about a foot in length) so that it moves in a circle (on level ground) of radius r (will be accommodating circles ...
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### what is the energy required to change only direction of a vector? [closed]

Does change in velocity vector change Kinetic energy of a system? Does any energy change when we change direction of a vector of a system?
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### graphical representation of Maxwell velocity distribution law

I have read Maxwell's distribution law it is the probabilistic representation of no. Of particles having velocity between $c$ to $c+DC$,through this representatation we can get the number of particle ...
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### Calculate the height reached when 1/3 of original Kinetic Energy is lost [closed]

I am sorry for asking this low level question but there is a confusion, I am not overcoming from hours. My book asks me to solve the following problem: When an object is thrown upward, it rises ...
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### 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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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### Uncertainty in Range of Projectile [closed]

If we are given that a projectile is launched with velocity 10m/s at an angle of $45^\circ$ and uncertainty in angle is of $0.5^\circ$ . What is the uncertainty in the range of projectile. The problem ...
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### 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 ...
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 ...