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Results tagged with homework-and-exercises
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user 57610
Applies to questions of primarily educational value - not only questions that arise from actual homework assignments, but any question where it is preferable to guide the asker to the answer rather than giving it away outright. Please READ THE GUIDANCE IN META before asking homework-like questions.
3
votes
1
answer
1k
views
Forces acting on two balls in a jar [closed]
Consider the following situation:
Two balls are inside a jar with diameter $D$. The balls are uniform in mass and both have the same diameter $d$.
Express the forces that acts at the colored dots …
- 341
2
votes
2
answers
3k
views
Bungee jumping - find spring constant
A person of mass $m$ is attached to a spring that its loose length is $l_0$. He is standing on a bridge and jumps off it, so he travels down a distance $2 l_0$ when measured from the bridge up to the …
- 341
2
votes
0
answers
697
views
Relative velocity between a ball hitting a rod [closed]
A ball of mass $m$ travelling with a velocity $v_0$ collides elastically, and perpendicularly with a rod at a distance $d$ from the center of the rod. The rod has a mass $M$ and lies on a frictionless …
- 341
1
vote
1
answer
825
views
Pushing a crate on a friction floor [closed]
A man is pushing a crate at a constant velocity. there is a friction between the floor and the crate of $$\mu =0.41.$$ The pushing force is directed downward at an angle $\theta $ below the horizontal …
- 341
1
vote
1
answer
185
views
Projectile motion with drag force of the form $\vec f =-k \vec v$ [closed]
An object is fired with initial velocity $v_0$ at inclination angle $\theta$ above the horizontal. Drag force in the air is taken into account and is of the form $\vec f =-k \vec v$.
Knowing that the …
- 341
1
vote
4
answers
129
views
Approximations of the kind $x \ll y$ [closed]
I have an expression for a force due to charged particle given as
$$F=\frac{kQq}{2L}\left(\frac{1}{\sqrt{R^2+(H+L)^2}}-\frac{1}{\sqrt{R^2+(H-L)^2}}\right) \tag{1}$$ where $R$, $L$ and $H$ are distance …
- 341
1
vote
Is it possible to determine particles' velocities from their crossings on a ring?
I am thinking about a simpler approach:
Let $\vec r_1 $ and $\vec r_2$ be the position vectors of the two particles.
The particles move on a circular ring so that the vectors will look like $$\vec r_i …
- 341
1
vote
2
answers
2k
views
Throwing baseball at a car
For some odd reason, you decide to throw baseballs at a car of mass $M$, which
is free to move frictionlessly on the ground. You throw the balls at the back of
the car at speed $u$, and at a ma …
- 341
1
vote
1
answer
67
views
A sailboat and wind, to find $v(t)$
Consider a sailboat of mass $m$ that lies on still water. A wind blows the sailboat with velocity $v_w$ perpendicular to the sailboat. If the boat has a sail with area $A$, and the air density is $ …
- 341
1
vote
1
answer
1k
views
Accelerated wedge [closed]
Consider the following figure, where a mass $m$ is placed on a wedge which is accelerated to the right ($\vec a$) which could be negative.
The coefficient of friction between the mass and the wedge i …
- 341
1
vote
2
answers
2k
views
Number of revolutions of a rolling coin [closed]
Take two quarters and lay them on a table. Press down on one quarter so it cannot move. Then, starting at the 12:00 position, roll the other quarter
along the edge of the stationary quarter.
How many …
- 341
0
votes
1
answer
80
views
The meaning of $\vec {\dot r}$ in the solution of a particle's movement in the space
Suppose I have a charged particle $q$ with mass $m$, and an infinite long wire that lies on the $z$ axis, in which flows a constant current $I$. My ODE that describes its motion is
$$\vec {\ddot r}= …
- 341
0
votes
3
answers
13k
views
Topple a mass standing still
Consider the following situation:
This is taken from an example from my book with a solution.
The box weight is $W$ and the coefficient of friction between the floor and the object is $\mu$.
What …
- 341
0
votes
1
answer
240
views
The forces acting on 2 boxes [closed]
Consider the following figure:
The surface is not friction-less. When the force $F$ is applied on mass A: Is the force the mass A applies on mass B larger, smaller or equal then the Force that B e …
- 341
0
votes
1
answer
5k
views
The period of a mass-spring system including a pulley [closed]
A spring with spring constant $k$ is attached to a mass $m$ as illustrated in the following four set ups: Calculate the period of the motion for each of them.
In cases (1) and (2) the period i …
- 341