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7 votes
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How do I know if a motion is 1 dimensional or 2 dimensional?

Let's say you have the following motion (the red arrow) It looks 2D on this plot, since its motion changes both the $x$- and $y$-coordinates. However, if you redefine the axes like so: Then the ...
Allure's user avatar
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6 votes

How do I know if a motion is 1 dimensional or 2 dimensional?

Both you and your teacher can be correct depending on what you mean by "dimension." In everyday experience, we generally consider dimensionality to be the number of independent parameters ...
Roger Yang's user avatar
6 votes

What does it mean when vector quantity is negative?

$-\vec v$ is a vector which has the same magnitude as $\vec v$ but points in the opposite direction. So $\vec v + (-\vec v)=0$.
Dale's user avatar
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5 votes

How much time does it take for an object to fall from space?

If the body has no angular momentum (no tangential speed with respect to Earth), what you want to solve is Newton's second law in this form: $$m \frac{\mathrm d^2h(t)}{\mathrm dt^2}=-\frac{GMm}{(R_{\...
Mauricio's user avatar
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4 votes

How do I know if a motion is 1 dimensional or 2 dimensional?

One dimensional motion is any kind of motion that happens on a line. There are many ways to define this. For example, you could say that the position vector of the particle is always $\vec{r}(t)=r(t)\...
agaminon's user avatar
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3 votes

How much time does it take for an object to fall from space?

The solution can be found on Wikipedia, the time $\rm t$ to fall from $\rm r_0$ to $\rm r_1$ is $$\rm t=\left(\sqrt{\frac{{r_1} \left(1-\frac{{r_1}}{{r_0}}\right)}{{r_0}}}+arccos\left(\sqrt{\frac{{r_1}...
Yukterez's user avatar
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3 votes
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Is the answer given in the option wrong?

The answer sheet is correct. You are ignoring the statement “The direction of the motion of the object changed only once, at time t.” That means that the velocity was zero at time t. So before time t ...
Dale's user avatar
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2 votes

How much time does it take for an object to fall from space?

Assuming the fall is purely radial and neglecting any fancy rotation and coriolis effects, you would obtain a single differential equation: $$\frac{GM_e}{(R+h)^2} = -\frac{\mathrm{d}^2 h}{\mathrm{d}t^...
CompassBearer's user avatar
2 votes
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Work Done by kinetic friction in Circular Motion

In circular motion, your total displacement $$\oint \mathrm{d}\vec{s}$$ is zero, correct. But for work, you are not integrating just the displacement $\mathrm{d}\vec{s}$, but the quantity $\vec{F}\...
CompassBearer's user avatar
1 vote

How do I know if a motion is 1 dimensional or 2 dimensional?

the main thing take away: physics does not care a about your coordinates. So if the thing is moving on: $$ \vec r(t) = t\cos{\theta}\hat e_1 +t\sin{\theta}\hat e_2 $$ thats linear motion in a plane. ...
JEB's user avatar
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1 vote

Strain energy stored in a bungee cord pulled at its midpoint

When a spring is halved, its spring constant $k$ is doubled. Because I'm treating this as a two spring system I need to double the value of $k$ that I'm using. Using a value of $k=280$ N/m gives $x=....
Imperator's user avatar
1 vote
Accepted

How to calculate the relative speed when three bodies are involved?

Just draw a principal vector diagram of separate movements : Add $\vec B + \vec C = \vec C~'$ and you will get woman velocity relative to the ground. Now subtract that from train's A velocity vector ...
Agnius Vasiliauskas's user avatar
1 vote

Different results of Range of a projectile

This is a really weird question... You're talking about two entirely separate things. Usually when we refer to range, we mean the linear distance covered between point of takeoff and point of landing. ...
Ekarshi's user avatar
  • 63
1 vote

Different results of Range of a projectile

Your range equation assumes that the projectile stops at the same height it is launched at. If the launch angle is $0^\circ$, then it does not have an initial upward velocity component, and hence it ...
BioPhysicist's user avatar
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