Kinematics Definition and 1000 Threads

Homework Statement A welding robot consists of an arm (thin rod) that can rotate about the origin point O, and a welding tip, which can freely move along the rod, from the outermost point of the arm A all the way to the center point O. The design invokes two electric motors, one to turn the...

While reading through Kleppner & Kolenkow's "An Introduction to Mechanics," I realized something: I am horribly dissatisfied with their treatment of kinematics. Perhaps I am simply spoiled by more run-of-the-mill textbooks, like Tipler and Giancoli, but K&K seem to not give much attention to...

Homework Statement Particle X moves with a velocity of 15 m/s[R]. Particle Y moves with a velocity of 5.0 m/s[L]. What is the velocity of particle X with reference to particle Y? The correct answer is 20 m/s (R). I do not understand what velocity in reference to particle Y means, and how to...

Homework Statement Calculate the force of friction on a toy car as it rolls across a flat floor. Given: mass = 0.293kg time = 3.66 s displacement = 8.7Homework Equations Fnet = mass x acceleration displacement = [(velocity1 + velocity2)/2] time velocity2 = velocity1 + acceleration(time)The...

This is a small question about the actual number of kinematic equations. I've seen many websites derive 4 different equations, but some only use 3. The 4th equation that I have yet to see be put to use is xfinal=xinitial+1/2(vinitial+vfinal)(time) Could someone explain why some do not mention...

Question: At what angles must be the two forces ##\vec A+\vec B## and ##\vec A-\vec B## act so that the resultant may be : $$\sqrt{ A^2+B^2}$$ Attempt at solution : Let the given forces be ##\vec F_1=\vec A+\vec B## and ##\vec F_2=\vec A-\vec B## . Now, Resultant vector : ##\vec F_1 + \vec...

Wouldn´t it depend on the gun and the speed of its "bullet"? Not sure what this question refers to.

Homework Statement Problem reads: In reaching her destination, a backpacker walks with an average velocity of 1.34 m/s, due west. This average velocity results because she hikes for 6.44 km with an average velocity of 2.68 m/s, due west, turns around, and hikes with an average velocity of 0.447...

Hey, I've been lurking in the forums for a while and would still consider myself pretty new to the forums. I just want to know how many of you guys ride a motorcycle? What is your favorite style? How many of you know too much kinematics in order to ride a motorcycle safely? :DD Also how many...

Homework Statement A ##1.50## kg snowball is fired from a cliff ##12.5##m high with an initial velocity of ##14.0## m/s, directed ##41^{\circ}## above the horizontal. How fast does the ball travel when it hits the ground. Homework Equations ##E=K+U## ##V^2_f=v^2_i+2a(y_f-y_i)## ##y_f=v_i \sin...

haruspex submitted a new PF Insights post Frequently Made Errors in Mechanics - Kinematics Continue reading the Original PF Insights Post.

Homework Statement This is the final part of the problem so I won't give it exactly unless requested. The relevant information thus far is that astronaut George is traveling at ##(21i + 42j)ms^{-1}## relative to astronaut Sandra and he is at position ##(1260i + 2520j)m## from her. Sandra has...

Hello community. I have a task from my college and no matter how hard i tried i failed to find a solution for it. The task itself is resolvable (by drawing) but i can't figure the mathematical way to solve it. And it bothers me so bad. Homework Statement So i have this kinematics mechanism...

If you know the position vectors of a particle at two points along its path, change in time between the two positions, and the particle's velocity at the earlier point, what quantities can you calculate? a)average acceleration b)final velocity c)average velocity d)displacement My answer was...

Hi, Please explain what is the difference b/w kinematics friction and static friction ? Please explain, what is rolling friction ? Is it when we are pulling a weight with rope, and rope is rolling on a wheel ? for example in past days, people used rope to get water from well. Please explain...

Homework Statement The coordinate of an automobile in meters is x(t) = 5 + 3t + 2t2 and y(t) = 7 + 2t + t3, where t is in seconds. What is the instant acceleration of the car at time t = 2 s? ANSWERS: A. 10.2 m/s2 B. 9.5 m/s2 C. 7.9 m/s2 D. 15.0 m/s2 E. 12.6 m/s2 Homework Equations ains =...

Hi there, In a two body decay process like ## B \to l \nu ##, there is a factor ##| \bar{l} (1-\gamma_5)\nu|^2 ## in the matrix element amplitude, in which equals ##| \bar{l} (1-\gamma_5)\nu|^2 = (/\!\!\! p_l+m_l) (1-\gamma_5) /\!\!\! p_\nu(1+\gamma_5) = 2(/\!\!\! p_l+m_l) /\!\!\...

Homework Statement A train starts from a station with a constant acceleration of at = 0.40 m/s2. A passenger arrives at the track time t = 6.0s after the end of the train left the very same point. What is the slowest constant speed at which she can run and catch the train. Sketch curves for...

Homework Statement a) A fishing boat of mass m moves through water in the +x direction. At time t = 0, it is at location x = 0 and has speed v0 at that precise moment, the boat’s captain turns off the engines and let's the boat drift. Taking the drag force into account, Fd=-Kv^2, calculate the...

Homework Statement 2. An elevator ascends with an upward acceleration of 4.0 ft/s2. At the instant its upward speed is 8.0 ft/s, a loose bolt drops from the ceiling of the elevator 9.0 ft from the floor. Calculate: a. the time of flight of the bolt from ceiling to floor. b. the distance it has...

Homework Statement There are two train stations, 2.5km (2500m) apart, therefore an ordinary suburban train cannot reach its max v between the two station. They try to minimise time taken by accelerating at a constant rate of 0.1ms-2 for time t1 and decelerate at 0.5ms-2 for time t2. Find the...

John runs at 5 m/s joe runs at 3m/seg the distance to run is 300 m Antony in order to do the race more exciting allows john start t seconds after joe What is the t value so that the race finishes in a tie?? what distance was allowed to joe?? Answer 40 seg and 120 m I don't know how to denote...

Homework Statement A boy standing in an elevator accelerating upward throws a ball upward with a vo. The ball returns to his hands after time t. The acceleration of the lift isHomework EquationsThe Attempt at a Solution After time t, displacement of the ball = displacement of the lift vo t -...

Homework Statement An automotive test track forms a curve in the horizontal xy plane specified by y(x) =γx^3 / 2 where γ = 0.2 m^-1/2 and x ≥ 0 . A car moves along the track, starting at rest at the origin at time t = 0 , and picking up speed in accordance with v = ct , where c = 4.8 m s^-2 ...

Hello everyone, I am a just now starting to study physics and I am quite the newbie, but I am loving it! I am not doing this for school, I study as a hobby in my spare time, but I imagine this is the right place to post this exercise anyway! Here it is: We have a rock dropped from a cliff that...

Homework Statement I need to find velocity v from the drawing. Homework Equations Equations of kinematics The Attempt at a Solution I found that v=12.134 m/s . I need to know is it correct. [/B]

Homework Statement A crate of mass 9.2 kg is pulled up a rough incline with an initial speed of 1.52 m/s. The pulling force is 110 N parallel to the incline, which makes an angle of 20.6° with the horizontal. The coefficient of kinetic friction is 0.400, and the crate is pulled 4.94 m. (e)...

Homework Statement Imagine this: A rod is attached at one end to a rotating shaft. So, as the shaft rotates from 0 to 90 degrees back-and-forth (in the xy plane), so does the rod. My goal is to measure the instantaneous acceleration of the rod while its moving. I have a few 3-axis...

Consider a simple textbook problem in two dimensional kinematics - say, a projectile motion problem. I know that the x- and y- components of motion are independent of one another but I don't understand why. I know this is true due to everyday observation - empirical evidence of this being the...

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown > I'm studying for AP test. This is not a homework question. Does anyone know how to do number 2? I don't even know where to start. I tried factoring out t and using quadratic formula, but I kept...

Dear All, I am often get confused when four terms STATICS,DYNAMICS,KINEMATICS and KINETICS are used in physics Mechanics.can someone please differentiate between these four terms.i will be thankful.

Homework Statement "A person kicks a soccer ball at an angle 30° above the horizontal on the ground. The ball then hits a wall at an angle 15° below the horizontal 4.9 seconds later. Determine the height at which the ball hit the wall." (Assume acceleration due to gravity is 9.80m/s2 [Down].)...

It it bad practice to consider values of ##r## that are greater than or equal to zero, while ignoring negative values? Do I lose any information in my analysis of motion? I understand what values of ##r < 0## represent, and I'm willing to use them in a pure mathematics context. In classical...

Homework Statement Hi everyone, I am doing a lab currently (and it looks like a few other people on here have had similar questions...) and I'm having trouble with one of the concepts. I had to drop a ball from a height and measure the movement with a motion sensor, which was graphed with the...

Homework Statement A circular space hotel in orbit around the Earth has a radius of 220m. in order to produce "fake gravity" along the outer rim, it is desired to rotate at a speed that will produce a centripetal acceleration of 9.81 m/s^2. A) find the tangential speed of appoint on the rim...

In cases like projectile motion, although the acceleration vector is constant (ignoring air resistance), a single coordinate axis fails to describe the motion of the particle, since it occurs in a plane; therefore we need a minimum of two coordinate axes to fully describe the trajectory of that...

1. A cat walks in a straight line, which we shall call the x-axis with the positive direction to the right. As an observant physicist, you make measurements of this cat's motion and construct a graph of the feline's velocity as a function of time the figure...

Homework Statement You place a m=2kg block at the bottom of a playground slide and give it a quick kick, giving it an initial speed of vi=12m/s. The slide is inclined at an angle of 35 degrees and the coefficient of kinetic friction between the block and the slide is mu_k=0.2. Use g=9.8m/s/s...

Homework Statement Justin is racing Mark. Justin accelerates from rest at the starting point at 1.2 m/s^2 [E]. Mark is still adjusting his equipment and 2.0 s later begins to accelerate at 1.5 m/s^2 [E]. Where and when does Mark catch up to Justin? Homework EquationsThe Attempt at a Solution I...

Homework Statement Two masses are placed on top of a building. The mass of one is twice the mass of the other. Both are dropped at the same time. Neglecting air resistance, which statements are true? 1. Both objects have the same potential energy at the top 2. Both objects fall with the same...

Homework Statement A ball launched from ground level lands 2.85s later on a level field 48 m away from the launch point. Find the magnitude of the initial velocity vector and the angle it is above the horizontal. (Ignore any effects due to air resistance.) Homework Equations...

Homework Statement A soccer ball is kicked from the ground at an angle of 30◦ with speed 30m/s. Determine the duration of the flight, range and maximal height of the trajectory. Homework EquationsThe Attempt at a Solution 1. Break down the velocity vector into x and y components: 30cos(30) =...

Homework Statement A robotic bug is moving along the x-axis. Its equation of motion is x(t) = 10*t^2- 4*t - 6 I have a problem with only one question: What is the distance covered by the bug between t = 0.1 s and t = 0.4 s? Homework EquationsThe Attempt at a Solution [/B] The first...

A truck and a car both start from rest at the same time on a straight track. The car is 25.0 m behind the truck at the start. The truck accelerates at 3.70 m/s^2 and the car accelerates at 4.40 m/s^2. How long does it take for the car to catch up to the truck? Hey all, first post, didn't think...

Homework Statement So I am stuck on this homework problem. I understand the general direction I have to take, but my algebra and physics aren't good. Here's the problem: A simple Atwood's machine uses two masses, m1 and m2. Starting from rest, the speed of the two masses is 10.0 m/s at the end...

Homework Statement Block B has acceleration of 4 m/s2... Relative acceleration of block A w/ respect to B is 4 m/s2. Find magnitude & direction of accel for A? Homework Equations a_A = a_B + a_A/B x_A = x_B + x_A/B y_A = y_B + y_A/B The Attempt at a Solution x & y components: -4cos(20) =...

Homework Statement : Block B has acceleration of 4 m/s2... Relative acceleration of block A w/ respect to B is 4 m/s2. Find magnitude & direction of accel for A?[/B] Homework Equations a_A = a_B + a_A/B[/B]The Attempt at a Solution a_A = 4 +4 = 8 m/s2 <-- 8*cos(20) = 7.52 (x-component)...

Homework Statement A ship is traveling across the sea when its engines are cut. The ship slows down by a = -kV2. The ship gradually slows down from 5 knots/h to 12 knots/h over 20min. Determine the distance traveled in nautical miles. One knot is 1 nautical mile per hour.Homework Equations...

Homework Statement In which case car engine must do more work: To start driving from 0 kmph until car reaches 27 kmph or to reach 54 kmph from 27 kmph? Force of resistance in both cases are equal. I need to base answer of this problem on formulas. I apologize for any grammar mistakes (i'm not...

Homework Statement A lift ascends from rest with uniform acceleration of 4m/s², then it moves with uniform velocity and finally comes to rest with uniform retardation of 4m/s². If the total distance covered during ascending by the lift is 28m and the total time for ascending 8s respectively...