Kinematics Definition and 1000 Threads

Homework Statement A parachutist bails out and freely falls 59 m. Then the parachute opens, and thereafter she decelerates at 2.7 m/s2. She reaches the ground with a speed of 3.1 m/s. (a) How long is the parachutist in the air? (b) At what height does the fall begin? Homework Equations...

Homework Statement In the figure here, a red car and a green car move toward each other in adjacent lanes and parallel to an x axis. At time t = 0, the red car is at xr = 0 and the green car is at xg = 223 m. If the red car has a constant velocity of 20.0 km/h, the cars pass each other at x =...

Homework Statement In the figure here, a red car and a green car move toward each other in adjacent lanes and parallel to an x axis. At time t = 0, the red car is at xr = 0 and the green car is at xg = 223 m. If the red car has a constant velocity of 20.0 km/h, the cars pass each other at x =...

Homework Statement You drive on Interstate 10 from San Antonio to Houston, half the time at 58 km/h and the other half at 103 km/h. On the way back you travel half the distance at 58 km/h and the other half at 103 km/h. What is your average speed (a) from San Antonio to Houston, (b) from...

Homework Statement Calculate the average velocity after 11 s. Homework Equations v=d/t The Attempt at a Solution I need to find the total displacement to find average velocity. I assumed the displacement was -4 as the graph goes up then back down to 0 then -4 so total is just -4. Is that a...

Homework Statement A pilot is flying from City A to City B which is 300 km [NW]. If the plane will encounter a constant wind of 80 km/h from the north and the schedule insists that he complete his trip in 0.75 h, what air speed and heading should the plane have? Homework Equations v=d/t The...

Homework Statement : The trajectort of two projectiles are shown in the figure. Let T1 & T2 be the rime periods and U1 and U2 be their speeds of projection. Then(state the answer with REASON): A) T2 > T1 B) T1 = T2 C) U1 > U2 D) U1 < U2 [/B] (MAYBE, MORE THAN ONE CORRECT) Homework Equations...

Homework Statement : The trajectory of a projectile in a vertical plane is y = √3 x - (1/5)x2, where x and y are respectively horizontal and vertical distances of the projectile from the point of projection. Find the angle of projection and speed of projection.[/B]Homework Equations ...

Homework Statement : Question 1: A body is projected with speed u at an angle theta with the horizontal. Find the change in velocity in time t. Question 2: A body is projected with speed u at an angle theta with the horizontal. Find the speed of body at a height h. Both the questions are...

Homework Statement : A body is projected with 50m/sec at an angle of 53 degree with the horizontal. After what time velocity makes an angle 33.7 degree with horizontal. (tan 33.7 = 2/3)[/B] Homework Equations : Mostly from 2-Dimension and maybe calculus.[/B]The Attempt at a Solution : I've...

Homework Statement In the arrangement as shown in the figure below, the ends P and Q of an inextensible string move downwards with uniform speed u. Pulleys A and B are fixed. Mass M moves upward with a speed: a. 2ucosθ b. u/cosθ c. 2u/cosθ d. ucosθ Homework Equations None, I am not sure...

Homework Statement I was wondering that, if you are standing above a bridge with a height h and throw a rock in your hand with mass m and initial velocity v naught of 0, could you calculate how big of a splash said rock makes when it hits the water? Homework Equations Not sure, I'm guessing...

Homework Statement http://imgur.com/BPPbwpu Homework Equations s = ((v + u)*t)/2 - an equation of motion for constant acceleration, which is applicable in this situation. The Attempt at a Solution Let u be the velocity at which the projectile was launched. It is given that sx = symax. So...

Homework Statement [/B] A boy drops a 0.10 kg stone down a 150 m well and listens for the echo. If the speed of sound is 343 degrees Celsius, the how long after the stone is dropped will the boy hear the echo? Homework Equations v = d/t v2 = v2 + 2ax The Attempt at a Solution [/B] What I...

I'm a junior in physics, and I had a really embarrassing experience lately with some freshmen. Basically, within the major I have earned straight A's in all my physics courses since freshman year, I'm the student body president of the physics majors, and I'm doing a summer REU at one of the...

So, you'll have to forgive me, but I am an engineer, not a physicist, but I take an interest in quantum gravity. My understanding is primarily conceptual, not mathematical. So if my question is dumb, I apologize. Ok, here goes: I'm aware of Zwi Bern's conjectured color-kinematics duality...

Homework Statement A person is standing over a well and drops a rock. After 2.4 seconds he hears a rock splashing into the water. Take the speed of sound to be 300m/s and calculate the depth of the well. Homework Equations x=v/t for constant velocity x=1/2at^2 for accelerated motion The...

Homework Statement L=18ft , theta-dot=8rpm or .83776 rad/s, omega = 1 rad/s, fi-0=70.5 and fi-1=24 Homework Equations - 3D motion[/B]The Attempt at a Solution I have come up with a ton of different answet inbetween 12-18 ft/s^2. Non have been correct[/B]

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 >[/color] 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...

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...