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.

learn more… | top users | synonyms

7
votes
4answers
648 views

What's my weight when jumping on a bicycle from a higher to a lower ground?

Before I start defining the situation and asking a question, I'd like to make a few things clear: this is not a homework, merely a matter of personal interest and enthusiasm I am neither a ...
7
votes
16answers
17k views

Recommendations for good Newtonian mechanics and kinematics books

What are some good books for learning the concepts of Kinematics, Newton laws, 2D Motion of Object etc.?
0
votes
1answer
176 views

When can I use equations of motion?

The three equations are: $$v = u+ at , $$$$s = ut + \dfrac{1}{2} at^2 , $$$$ v^2 = u^2 + 2as.$$ Can I use them for both finding instantaneous and average quantities? Suppose I want to find the ...
0
votes
0answers
28 views

How to calculate the equation of projectile motion for curved ramps? [duplicate]

Consider the following cases (these are sections): I can find the equation of motion for Case a however I don't know how to deal with Case d. Normally I would need the angle α otherwise I can't ...
2
votes
2answers
57 views

Jump of a mass and violation of physical laws

I've just watched one of Feynman's lectures on the character of physical law where he was talking about conservation laws. In that particular part he was reasoning why a mass can't "jump" from one ...
5
votes
4answers
989 views

How to tell if the collision is elastic or inelastic?

I'm a programmer and a game developer, not a mathematician or a physicist. So please go easy on the math :) I know two things: How to find the new velocities of two objects after an elastic ...
2
votes
3answers
2k views

Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?

Does an object's kinetic energy increase, decrease, or stay constant when it reaches terminal velocity while falling?
1
vote
0answers
58 views

Finding the time of convergence for this system of particles [closed]

Point A moves uniformly with velocity $v$ so that the vector $\vec{v}$ is continually "aimed" at point B which in turn moves rectilinearly and uniformly with velocity $u < v$. At the initial ...
3
votes
2answers
2k views

Proof of centripetal acceleration formula ($a_c = \frac{v^2}{r}$) for non-uniform circular motion

The formula for centripetal (radial) acceleration is well known, and there exist many proofs for it: $$||a_c|| = \frac{||v||^2}{r}$$ However, all the proofs I've seen rely on the fact that it is ...
0
votes
2answers
58 views

Isn't this statement regarding projectile motion wrong?

Isn't this statement regarding projectile motion wrong? If a body is thrown at an angle to the horizontal with initial velocity $u$, then displacement of body as a function of time is ...
2
votes
1answer
90 views

Why speed of Mangalyan is constant?

I have learned in school regarding the relationship between speed,acceleration and distance is $$v^2-u^2=2as $$ The initial velocity of India's Mars Orbiter Mission, MOM, is 32 km/s source and now ...
1
vote
0answers
43 views

Calculating size/weight of the base of a banner to withstand wind load [duplicate]

I want to build what is essentially a banner - a rectangular piece of fabric that will be mounted to a stand and displayed vertically. This object will be outdoors, so the most important factor in it ...
0
votes
3answers
2k views

Calculating acceleration function for given time, distance, initial velocity [closed]

An object has an initial velocity of v and should stop in d meters, in t seconds where v*t >= d. I can predict that this acceleration won't be constant but it is a function of time and this problem ...
1
vote
2answers
68 views

What's The Minimum distance?

My Friend gave me a question today. The question was.:: We have a point A. At a distance of $x_0$ from the point. There is a particle$(P_1)$. Also, a particle is present at the point A $(P_2)$.The ...
1
vote
1answer
115 views

Kinematics simple question [closed]

Question: In order to protect himself from the rain, a person is standing holding an umbrella at right angle to the horizontal surface. The rain is falling at 10m/s when the velocity of the wind is ...
1
vote
2answers
137 views

Why is the constant velocity model used in a projectile motion derivation?

I was re-studying university physics last week, I'm now in the chapter about kinematics in 2 dimensions and specifically the one treating projectile motion. In page 86 of his book (Serway - Physics ...
0
votes
2answers
44 views

Finding out the velocity [closed]

Displacement of an object is related to time $x=at+bt^2-ct^3$ where a, b and c are constant motion.Then the velocity of an object when it's acceleration is zero is given by ...
4
votes
2answers
682 views

Can these figures demonstrating the safety of “Archery Tag” arrows be correct?

There is a new sport called "Archery Tag" that involves shooting opponents with foam-tipped arrows fired out of a real bow. The official Archery Tag web site presents data that claims to show the ...
0
votes
2answers
1k views

Kinematics - projectile motion on inclined plane [closed]

Well I've tried everything to solve this problem, spent well over an hour, and have gotten no results. A particle is thrown over a triangle from one end of a horizontal base it grazes the top vertex ...
0
votes
3answers
116 views

Kinematics - Concept of average velocity

Average velocity, as I have heard, cannot be found simply by finding the average of two numbers. I have a question on average velocity, but am simply unable to proceed: A particle moving in a ...
0
votes
1answer
64 views

Kinematics - ball bouncing off vertical walls [closed]

So here's my best attempt to state the question: A ball is thrown from a 100 meter tall tower, which has a vertical wall in front of it. The initial velocity of the ball is 10m/s and the distance ...
2
votes
1answer
89 views

Kinematic, motion in 2D [closed]

If the kinetic energy at maximum height is 2/5 the kinetic energy at half the maximum height, find the angle of projection. In other words: K.E. at H(max) = 0.4*K.E. at 0.5*H(max) I got 60 degrees, ...
2
votes
1answer
93 views

Exeeding the speed of light by adding velocities [duplicate]

Well you know how it's said that things can't travel at or past the speed of light? However, can't they move at speeds greater than the speed of light relative to another object? For example: What ...
-4
votes
3answers
61 views

Velocity and acceleration with displacement [closed]

Find the velocity and the acceleration for a moving object with displacement $= te^{-t}$. The $e$ is the exponential function.
0
votes
0answers
40 views

Geometric Interpretation of these equations of motion?

I was reading my Engineering Mechanics book, and it derived some strange looking integrals I'll have to apply. I could memorize them, but I'd rather understand them - then I won't have to memorize. ...
1
vote
3answers
79 views

average speed and velocity [closed]

A distance on a straight line from point $a$ to $b$ is $2 km$. A student walks from this line with a speed of 4km/h and another student walks with a speed of 6km/hour. what is the average velocity and ...
1
vote
0answers
45 views

how to calculate acceleration? [closed]

The problem is as follows. A searchlight casts a spot of light along the face of a horizontal wall located 100m above from the searchlight. It rotates at a constant $\omega$ of 4rads/s. Determine the ...
1
vote
3answers
105 views

Uniform Circular Motion and Centripetal Acceleration

In introductory physics books (or at least mine) it limits the equation $a_c=v^2/r$ to the situation where the speed around the circular path is constant. It enforces the idea that the speed is ...
0
votes
1answer
51 views

Velocity at certain point?

I seem to have misunderstood something in velocity. There is a path from point A to point B, that gap between is 100 meters. An object moves from point A to B with a velocity is 10 m/s. ...
1
vote
1answer
71 views

Understanding why a problem was solved a certain way

I have this question in one-dimensional kinematics and the way the book solves it has left me confused. Here's the question: ...
1
vote
2answers
64 views

Why is initial position negative? [closed]

A student on ground throws a ball straight up, the ball leaves students hand with speed of 15m/s when hand is 2.0mm above ground How long is the ball in the air before it hits the ground? I was ...
0
votes
1answer
58 views

From 3D velocity to coordinates

I want to calculate the 3D position $T_x, T_y, T_z$ of an object with respect to a coordinate system if I have the mean velocity (norm) $v$ and its 3D rotation $(\omega, \phi, \kappa)$ with respect to ...
1
vote
4answers
392 views

Calculate average speed with unknown variable accelaration

I am in the middle of a vehicle tracking project where I have to calculate the distance traveled by the vehicle in a given amount of time. Data I am getting: ...
0
votes
2answers
65 views

Projectile motion - ball hit 180m/s at 45 degrees, what is the hang time? [closed]

Assuming no air resistance etc, how long is the ball in the air for? This is actually part of a longer question concerning the ball trajectory on different planets but I think there must be an easier ...
1
vote
1answer
69 views

Travel time for accelerating object [closed]

I have an object which starts at velocity = 0. Accelerates to a known max speed and continues thereon at constant velocity (max speed). My problem: How long does it take to reach a known ...
2
votes
1answer
51 views

The speed of an unconstant motion

There's already the solution for the problem but I still don't understand why the velocity can't be calculated by just $$ a = (v(t))'= -B_0 + B_1t \Rightarrow v(t) = -B_0t + 1/2B_1t^2$$ Also, both ...
1
vote
0answers
67 views

How makes an equation to Flipping motion

Every now and then, I find myself reading papers/text talking about how this equation is a constraint but that equation is an equation of flipping which satisfies this constraint. Indeed, This ...
2
votes
1answer
164 views

How to get time from equation of linear uniformly accelerated motion? [closed]

I have had a problem solving this equation for time (from Linear Uniformly Accelerated Motion (LUAM)): $$ s= v_0t + \tfrac{1}{2}at^2 $$ I'll appreciate if someone could provide me some step-by-step ...
2
votes
2answers
1k views

Average velocity = Arithmetic Mean

I am having trouble grasping how the average velocity of a particle between an initial position and final position equals to the arithmetic mean of the initial velocity and the final velocity when the ...
-2
votes
1answer
210 views

Kinematics - angle of projection given relation between speed at highest point and half of that [closed]

For a projectile launched from a point on horizontal ground, the speed when it is at the greatest height is $\sqrt{\frac{2}{5}}$ times the speed when it is at half of its greatest height. Determine ...
2
votes
3answers
687 views

Getting position from an accelerometer on an Android phone

I know that integrating acceleration twice will give me position (acceleration-->velocity-->position) but how can I do all this when I all I have are a set of data points (ex: 1 second = some # ...
3
votes
1answer
111 views

How to interpret $t^2$? [closed]

I can't think of the meaning of squaring the Time (multiplying it by itself). It makes sense in Mathematics. But how can you figure it out in nature (or physics). As an example, the formula ...
1
vote
2answers
180 views

Help with a solid sphere sliding and then rolling

Initially at time $t=0$, a solid sphere slides with velocity $v$ along a horizontal surface. The coefficient of friction is u. Find the required time for the sphere to stop sliding (the sphere will ...
0
votes
3answers
129 views

Displacement of a body in free fall

Suppose a ball is thrown up from the ground with some velocity. Let vertically up be the positive direction and vertically down be the negative direction and let the thrower be at the origin. What ...
8
votes
4answers
26k views

What is the relationship between kinetic energy and momentum?

I can't seem to figure out the relationship between $E_k$ and $p$ or $F$. I understand that the units are pretty different. But for example: A bullet with a mass of 10.0g is moving at the speed of ...
0
votes
1answer
2k views

How to find speed from Newton's law?

I have a question about Newton's law. The question says block A(mass 2.25kg) rests on a tabletop. It is connected by a horizontal cord passing over a light, friction less pulley to hanging block ...
5
votes
2answers
13k views

Difference between momentum and kinetic energy

From a mathematical point of view it seems to be clear what's the difference between momentum and $mv$ and kinetic energy $\frac{1}{2} m v^2$. Now my problem is the following: Suppose you want to ...
-3
votes
1answer
347 views

Throwing an object in the air [closed]

Studying formulas about velocity and acceleration I came up with a question: if I throw an object in the air with a velocity $v_0$ (suppose i throw it vertically) in how much time its final velocity ...
2
votes
3answers
83 views

How to calculate the velocity of this body? [closed]

Graph of a train (the body) is provided which starts from rest. What is the velocity after the train has 10 metres displacement? Thats the only things provided for the question, please help me ...
0
votes
2answers
164 views

Is there a mistake in this example in my mechanics textbook?

This is a worked example in my mechanics book: But I think this worked example is wrong. In the 6th line. shouldn't $X=4R$ as the expression for distance above the surface is $(X-R)$ and when the ...