# Questions tagged [kinematics]

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.

3,402 questions
Filter by
Sorted by
Tagged with
12 views

### Calculate Torques & Forces From Jacobian Matrix

Dear Physics Stack Exchange, I am trying to calculate the torques and forces for a 2DOF robot. I’m used the partial differentiation method to find the Jacobian matrix. I managed to find the ...
30 views

### Can accelaration of a falling mass be positive when upwards direction is positive? What am I missing?

As shown in the figure: (+) direction is upwards displacement is y time=t Let's say that $y=30-5t^{2}$ , thus the second derivative will give acceleration as -10 which is (-) as expected. Now let'...
21 views

### Does tension vary across length of rod when there is no acceleration?

I know that Tension $T$ across elements of rod will vary in the case when the rod is moving with acceleration, and for each element tension acting will be equal to $ma$ (towards left) where $a$ is the ...
53 views

### Apparent wavelength received by observer in doppler's effect

I have a few doubts about Doppler's effect. Does the apparent wavelength received by the observer depend upon whether the observer is moving or not? $λ_{apparent}=\ \frac{v_{sound}\pm v_{source}}{f}$....
74 views

### How to derive 3rd equation of motion $v^2=u^2+2as$ using $F=ma$?

How shall I derive, $v^2=u^2+2as$ using the equation $F=ma$?
68 views

### When to use relative velocity in centre of mass problems? [closed]

I am confused about when we should use relative velocity of an object placed on a movable platform like a wedge while solving center of mass related dynamics problems. For example, in the first ...
33 views

81 views

### Do conserved quantities tell us more general pattern than what we are taught?

Last year I had a question in m mind that as $mv$ (momentum) and $mv^2/2$ (Kinetic energy) both are conserved then n a closed system and they are dependent on same quantities and look very similar so ...
48 views

### Rendezvous between two accelerating objects from opposite sides [closed]

I have two objects. Object 1 is travelling from A to B, a distance of (let's say) 1,000,000km. It can accelerate at 2g, and will accelerate up to the halfway point and then decelerate until the end (...
73 views

### What is the speed of a satellite?

Linear velocity $v$ is by definition the runned space $ds$ per time $dt$ elapsed: $v=ds/dt$. If the time elapsed in a specific point on the earth's surface is $t$, the dilated time elapsed on ...
41 views

### How do we implement the speed differential for the Ackermann steering?

I'm working on a vehicle that uses four independent motors to control both the steering and speed for each wheel. I'm using Ackermann steering, and I've already got the steering angles down for the ...
32 views

### How do you calculate the minimum velocity for this problem? [closed]

I need help with the question below. I have started with that the distance travelled in the x - direction has to be greater than 2R and the same goes for in the y - direction. I then used the ...
71 views

### When is $a_c = v^2/r$ valid?

All the derivations I've seen of the formula in the title, namely $a_c = \frac{v^2}{r}$ rely on the tangential speed $v$ being constant. However, I watched this video: https://www.khanacademy.org/...
If $E= mc^2$ then c = $\pm \sqrt{E/m}$. What is the real world meaning for a negative speed of light ? Anything traveling faster than $-300k m/s$ is travelling faster than the speed of light ? What ...