All Questions
Tagged with time homework-and-exercises
101
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2
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102
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What to do when the time interval is negative? Should its magnitude only be considered or should it be rejected?
Two bodies are dropped from the same point at different times. I am asked when they meet. The answer I get is -4 seconds. How do I interpret this?
I think that a time interval $t_2-t_1$ always has to ...
- 21
-5
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1
answer
74
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Reality of speed and time [closed]
I have a very simple question. How does a faster object takes less time for the same distance? A car with a speed of 100km per hour takes one hour to travel 100km while a car with the speed of 50km ...
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33
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I need a ship at rest to accelerate under preferably constant acceleration/deceleration to arrive at rest at an object 55 AU away [duplicate]
I'm working on the story and I need help with the plot point. Assume that the energy needed for constant acceleration is not a problem. And there's no need to complicate this with outside forces.
I ...
1
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How to derive the period of non-circular orbits? [closed]
By conservation of mechanical energy:
$$
E(r_0)=-\frac{GMm}{r_0}+\frac{1}{2}\mu \left (\dot{r_0}^2+r_0^2 \omega_0^2 \right)
$$
where $r_0 =r_{max}$. Because our body is located at the apoapsis: $v_r = ...
- 1,525
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481
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Effect of the length $\ell$ on a pendulum
Currently, I am trying to intuitively understand how the length $\ell$ affects the period of a pendulum. I understand that the shorter the length $\ell$, the shorter the time period $T$. When we have ...
- 53
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2
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166
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Commutator of energy and unitary time evolution operator
Edited:-
$\hat{H} = -\frac {\hbar^2}{2m} \frac {\partial^2}{\partial^2 x}~+~V$
$\hat{U}(t) = e^{-iHt/\hbar}$
The Robertson Uncertainty Principle states:-
$\sigma^2_A\sigma^2_B \ge (\frac {1}{2i}[\hat{...
user355398
14
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A paradoxical problem in Classical Mechanics
In Kibble-Berkshire Classical Mechanics there is a problem which says:
A ball is dropped from height $h$ and bounces. The coefficient of restitution at each bounce is $e$. Find the velocity ...
- 331
1
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3
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281
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Can the age of the universe actually be calculated through Hubble's constant?
I was reading a high-school physics textbook, and it stated that the age of the universe is equal to 1 / Hubble's constant. They even give a derivation: $v = H_{0} D$ and $D = vt$, so subbing in gives ...
- 25
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135
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When will the 2 cars Have equal speeds? [closed]
If car1 started at 20m, with initial velocity of -4m/s and acceleration of 3 m/s^2.
Car 2 started at 15m, with initial velocity of 6m/s and acceleration of 0. At what time will the 2 cars have equal ...
- 103
3
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235
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Why does it take $2d/\lvert v_1 - v_2\rvert$ time to overtake? (Can physics catch-up to math?)
The following answer is from this post.
So it becomes particularly easy to see that the opposite-direction meetings must occur at the interval $2d/(v_1 + v_2)$ and that the overtaking meetings must ...
- 177
2
votes
0
answers
71
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Number of meetings of $2$ cars starting from opposite ends of a road [closed]
Question:
$2$ cars travelling at $108,75$ kmph respectively, start from the opposite ends of a $90$ km straight road. Travelling back and forth continuously for $10$ hours, how many times do the $2$ ...
- 177
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79
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Why do my equations say that an object thrown at $30^o$ with velocity 30 m/s has a $y$ velocity of 15 m/s? [closed]
I don't know if I have stumbled upon a genuine truth, or if I'm doing something very wrong. But here is my problem:
I am modelling the 2D trajectory of an object with constant acceleration using ...
- 309
2
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1
answer
161
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Clarification on clock synchronization passage from Kleppner and Kolenkow
I have a question about the following passage from An Introduction to Mechanics by Kleppner and Kolenkow. The passage reads as follows:
The Newtonian procedure would work if the speed of light were ...
0
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1
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55
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The probability of a circular region being "invaded" by moving spheres as a function of time
I had uploaded the same problem in maths stack exchange but since it got no answer and because I think that it is a problem that can be seen both as a physical one I considered uploading it both on ...
- 331
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Gravitational collision [duplicate]
Two point particles of exactly the same m = mass 1kg is separated by a distance of d = 4m. After how much time, they will collide with each other due to the force of gravity?
Assume that, the ...
