# 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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### Kinematic problem (initial acceleration)

A ball is rolling over a soccer field with constant velocity $V_{b} > 0$ at an angle of 45° to the goal line. It starts at the corner of the field (distance $d$ from the middle of the goal line) at ...
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### Calculation of stone dropping [on hold]

A stone dropped from a building of height $h$ reaches the ground after $t$ seconds in the air. From the building top, if two stones are thrown, one upwards, the other downwards, with same velocity $u$...
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### Linear motion in a constant acceleration [on hold]

a car start to move from rest and travels along a straight horizontal road with a constant acceleration. Velocity of the car after t seconds is vms-1. Find the displacement of the car during the ...
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### Calculating resultant force along vertical axis when using smartphone accelerometer [on hold]

I'm making an app which is using accelerometer to automatically detect damages on the route while driving. To estimate if damage occurred or not I'm using accelerometer (acceleration along vertical y ...
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### Kinematics of Rectilinear Motion [on hold]

A car leaves an outpost and reaches a speed of $60 m/s$ with a constant acceleration of $3 m/s^2$. It continues at this speed for a time then decelerates at $4.2 m/s^2$. How far will the car be after ...
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### High School Physics [on hold]

Two girls are standing on a bridge over a river. One girl falls freely and the other ties a rope to her legs. Both jump at the same time from the bridge. The length of the rope is more than the ...
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### Kinetic Hysteresis [duplicate]

I have been wondering about this question for quite some time, but, until now, I was not sure how to phrase it without sounding naïve. Let's take Newton's Cradle (just three congruent balls will do). ...
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### Initial Velocity Question

What is the initial velocity vertically when a person jumps 0.5 metres into the air, neglecting horizontal movement. Is it just 0 m/s? And the final velocity would be -9.8m/s^2 * the time it took took ...
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### Horizontal Velocity of a Projectile thrown from a Cliff [on hold]

If I were to throw a rock of a cliff at 12 m/s as a horizontal velocity, what will the final velocity of the rock become when it hits the ground? I am tempted to say 12 m/s because the horizontal ...
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### Motion in a Plane Question [on hold]

I don't understand how to do this problem: You are the pilot of a small plane and want to reach an airport, 600km due south, in 4.0h. A wind is blowing at 50km/h[S35oE]. With what heading and ...
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### Vertical Motion Question [on hold]

Question: An object is projected vertically to to the ground in a 20 m/s velocity. After 3 seconds another object is projected from the same position in the same velocity to the same direction. ...
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### Analysing kinetic energy in different frames [duplicate]

Case A: Say we observe a body X moving with a velocity of 30 on the +x and we(the observer) are stationary. Case B: The observer moves with a velocity of 50 on the -x. The body X is moving in the ...
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### Pls help me visualise this situation, I'm not able to understand it [on hold]

Find time of flight of projectile thrown horizontally with speed 50m/s from a long inclined plane which makes an angle theta= 45° from horizontal.
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### Movement of a box containig a particle [closed]

A small thought experiment: Imagine a rectangular box in space, containing particle, all resting at $t=0$ from your point of view. At some point in time $t>0$ the particle starts to move with ...
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### Projectile motion and bouncing [closed]

Prove that the number of bounces n after throwing an elastic ball on a frictionless surface with a known angle (j)relative to the horizon and the angle of the initial velocity is known also (k)..is ...
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### projectile on an inclined plane [closed]

Is the time of ascent equal to the time of descent? I tried it but I am not being able to prove it mathematically.
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### I don't understand the approach used in solving this kinematics problem

The problem text is as follows: During the first half of a straight path, which is at $\alpha_1=60°$ relative to a reference line, a car is travelling at $v_1=72 km/h$. During the second half of the ...
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### Differential velocity and acceleration [closed]

A particle moves along the curve $X = 2\sin3t$, $Y = 2\cos 3t$, $Z= 8t$ How to find the velocity and acceleration when $t>0$?
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### Can one rise through a free-falling rope?

I am a little confused about this question. I cannot imagine that it is possible to rise through a rope (assuming inextensible) that isn't fixed in its upper end. But when I solve this problem, I see ...
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### Why is the sign of the tangential component of acceleration negative in this problem? [closed]

Since the train is slowing down at a constant velocity, shouldn't the acceleration equal zero? Why is it negative in this case?
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### Acceleration at rest when ball is thown [duplicate]

If a ball is thrown vertically upward and it comes to rest for a moment, then its velocity decreases and becomes zero. Does its acceleration also becomes zero? If yes then how ball falls down?
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### Can a system's internal forces change the system's motion?

Let say the motor makes the two rigid body rotate as a same velocity. (they rotate the opposite direction) then the Net force of the motor is 2Fsin(Theta). The acceleration of the motor is 2Fsin(theta)...