Mechanical energy Definition and 354 Threads

Homework Statement Consider a pendulum bob swinging. The bob follows a circular path which indicates that gravity is not the only force acting upon it. Identify the additional force; does it affect the equation K + U = 1/2 mv2 + mgh? why or why not? The Attempt at a Solution First i cannot...

A toy cannon uses a spring to project a 5.30 g soft rubber ball. THe spring is originally compressed by 5.00 cm and has a force constant of 8 N/m. When the cannon is fired, the ball moves 15.0 cm through the horizontal barrel of the cannon and the barrel exerts a constant friction force of .032...

Homework Statement A 700 g block is released from rest at height h(not) above a vertical spring with spring constant k= 400 N/m and negligible mass. The block sticks to the spring and momentarily stops after compressing the spring 19.0 cm. How much work is done (a) by the block on the spring...

Homework Statement a 6.0kg concrete block is dropped from the top of a tall building. the block has fallen a distance of 55 meters and has a speed of 30 meters per srcond when it hits the ground 1) at the instant the block was released what was the gravitational potenetial energy with...

1. Homework Statement A 0.50 kg rubber ball is thrown into the air. At a height of 20 m above the ground, it is traveling at 15 m/s. a. what is the balls kinetic energy b. What is its gravitational potential energy relative to the ground? c. how much work was done by someone at ground level...

Please help... with Mechanical Energy Question Homework Statement A 0.50 kg rubber ball is thrown into the air. At a height of 20 m above the ground, it is traveling at 15 m/s. a. what is the balls kinetic energy b. What is its gravitational potential energy relative to the ground? c...

(wasn't sure if I should post this in the general physics or in the "homework" forum... this question is loosely based on a problem found in a printed book, but I have modified it myself... regardless, here is the situation) Homework Statement A person is sliding down a frictionless...

A pendulum was set up and measurements were made to enable the mechanical energy to be calculated at the start position S and the lowest point of the pendulums swing L. The mass of the pendulum bob was determined on an electronic scale and its diamter was measured using calipers. The initial...

I have a problem with my train of thought. I have narrowed it down to several premises, and I think that one of them must be wrong. Premise 1 Δ total energy (E) = Δ kinetic energy (K) + Δ potential energy (U) (assuming that there is no change in any of the other forms of energy in the...

Suppose we have a universe consisting of three planets. Their velocities and positions at t=0, and the gravitational constant are known. One can calculate, using differential equations, the positions of the planets at any time. Assuming that the only force acting on the planets is gravity and...

Homework Statement A 70.0 kg base runnner begins his slide into second base while moving at a speed of 4.0m/s. The coefficient of friction between his clothes and Earth is 0.70. He slides so that his speed is zero just as he reaches the base. A) How much mechanical energy is lost due to...

Homework Statement The nominal food-energy value of 1.00g of butter is about 7.20 food calories. If all this energy could be converted completely to mechanical energy, how much butter would be required to power a 65.0kg mountaineer on her journey from Lupine Meadows (elevation 2070m) to the...

Homework Statement A 42 kg child on a 2.3 m long swing is released from rest when the swing supports make an angle of 32 degrees with the vertical. The acceleration of gravity is 9.8 meters per second squared. If the speed of the child at the lowest point is 2.34094 m/s, what is the...

Homework Statement at a lake hangout there is a tree to swing from over the lake.. Friend is scared and doesn't let go and swings back and forth severall times without stopping. Is his mechanical energy conserved during the swinging process? Homework Equations The Attempt at a Solution

Homework Statement The figure shows a block on a frictionless surface attached to a spring. The block is pulled out to position x_i = 20 cm, then given a "kick" so that it moves to the right with speed v_i. The block then oscillates with an amplitude of 44 cm. Image of the problem -...

Mechanical Energy of Amonia Molecule [SOLVED] Homework Statement The ammonia molecule has the tetrahedral structure shown in the figure (Intro 1 figure) . The three hydrogen atoms form a triangle in the xy-plane at z = 0. The nitrogen atom is the apex of the pyramid. The figure (Intro 2...

Is momentum always conserved when total mechanical energy is conserved? My understanding is that this is false, but unsure.

1.A chain on top of a table is stretched out in a straight line perpendicular to the table's edge with one fourth of its length L hanging over the side. How much work is required to pull the hanging section of the chain back into the table. (hint: divide the hanging part into segments of length...

A 48.0 kg block slides along the frictionless surface of a hill that is 188 m high with an initial speed 19.0 m/s. Relative to the bottom of the hill, (Note that the acceleration is not constant so you can not use freefall equations to solve the following problems.) What is the block's...

Homework Statement A 70 kg base runner begins his slide into second base when he is moving at a speed of 4.0m/s. The coefficient of friction between his clothes and the Earth is 0.70. He slides so that his speed is zero just as he reaches the base. a) How much mechanical energy is lost due...

[SOLVED-Thanks AL]Mechanical Energy loss due to NC Forces: two railroad cars collide. SOLVED! - Thanks Al![/color] Homework Statement Two railroad cars each of mass 4800 kg and traveling @ 80 km/h collide head on and come to rest. How much thermal energy is produced in this collision...

Ok so the rpoblem is A 2.20kg box slides down a rough incline plane from a height h of 1.63m. The box had a speed of 2.33m/s at the top and a speed of 1.90m/s at the bottom. Calculate the mechanical energy lost due to friction (as heat, etc.). and I am not sure where to even begin with this...

Homework Statement A 25.0 kg child slides down a long slide in a playground. She starts from rest at a height h1 of 19.00 m. When she is partway down the slide, at a height h2 of 6.00 m, she is moving at a speed of 9.10 m/s. Calculate the mechanical energy lost due to friction (as heat, etc.)...

Homework Statement In this era of high energy prices, there is a focus on renewable sources of energy such as wind energy. Consider a large windmill 30m in diameter. On a windy day, suppose that the windmill entrains a stream of air 25 m in diameter at a speed of 14 m/s. Downstream of the...

Homework Statement I have a doubt on total mechanical energy conservation in a non conservative system. I think, in such a system there are dissipative forces as a result of which the total mechanical energy is not conserved because there may be loss of energy in the form of heat or other...

Homework Statement I am having difficulty with the concept of a certain question from my textbook that goes as follows: Your friend's Frisbee has become stuck 16 meters above the ground in a tree. You want to dislodge the Frisbee by throwing a rock at it. The Frisbee is stuck pretty tight...

Homework Statement A 1.90 kg rock is released from rest at the surface of a pond 1.00 m deep. As the rock falls, a constant upward force of 3.80 N is exerted on it by water resistance. Let y=0 be the bottom of the pond. a) what is the rock's kinetic energy at the surface and at the bottom...

Homework Statement A satellite of mass m is orbiting the earth. The radius of the orbit is r_{0} and the mass of Earth is M_{e}. a. Find total mechanical energy. b. Now suppose that satellite encounters constant frictional force f which retards its motion. The satellite will spiral...

Homework Statement A 12000 kg car traveling at 10 m/s strikes and couples with a 6000 kg car at rest. What is the loss of mechanical energy in the collision? Answer is 200,000 J. Homework Equations I want to know HOW to arrive at the correct answer above. The Attempt at a...

What is the best and most practical way to transform particular mechanical energy into electrical energy.I am not quite familiar to physics so I' ll try to explain what I want outsider way. When I say"particular mechanical energy" I mean the energy consisting of many low power hits.One hit make...

Homework Statement A car, of mass 1100 kg, is traveling down a hill, inclined at an angle of 5o to the horizontal. The driver brakes hard and skids 15 m. The coefficient of friction between the tyres and the road is 0.7. Find the initial kinetic energy and speed of the car. Homework...

Homework Statement A mass-spring system oscillates with an amplitude of 3.30 cm. If the spring constant is 231 N/m and the mass is 537 g, determine the mechanical energy of the system. Homework Equations Mechanical energy is potential energy plus kinetic energy The Attempt at a...

Homework Statement We did something very similar to this in lab http://webenhanced.lbcc.edu/physte/phys2ate/2A%20LAB%20HANDOUTS/Moment%20of%20Inertia.pdf Use Work and Mechanical Energy to derive the expression for the experimentally determined moment of inertia. Homework Equations...

Hello, What would be a good definition of mechanical energy? I currently encounter the following two: 1) "Mechanical energy: energy that is mechanical" 2) "Mechanical energy: the sum of kinetic energy and potential energy." I am disatisfied with the first definition due to the obvious...

Homework Statement Starting from rest, a 5.0 kg block slides 2.5 m down a rough 30.0 degree incline in 2.0 seconds. Determine the following: a. work down by the force of gravity b. the mechanical energy lost due to friction c. the work done by the normal force between the block and the...

Homework Statement A 0.13 kg ball moves at a rate of 20.0 m/s at the point where it is 5.00 m above the ground. How much mechanical energy does the ball have with respect to the ground? Homework Equations Ek = 1/2mv^2 The Attempt at a Solution Ek = 1/2mv^2 Ek =...

Homework Statement A projectile with a mass of 20 g has an initial horizontal velocity of 100 m/s when it hits and stops in a wood block of mass 0.402 kg. The block is sitting on a horizontal frictionless surface and is attached to a massless spring, initially relaxed, with spring constant 143...

Homework Statement There is a rollercoaster. A car starts 35m "high" and descends to the ground. A.) What is the velocity at this point? The car continues an goes 28m above the ground. B.) calculate its velocity at this point. C.) If the car descends another 13m from this point, what is the...

Hi, I am a new PE member. I am not a physicist but would appreciate any and all assistance offered. I am attempting to calculate the quantity of mechanical energy available at an automotive shock absorber. The end result of this exercise would be to replace the existing shock with an...

Mechanical Energy question (Skier going down a slope...confusing!) First of all, I apologize ahead of time if my question seems to be really simple, but I have been working on it for at least two hours and still no progress (which is why this post made so late lol). My class has been working on...

Alright I have a few problems here. 1). A bird is flying with a speed of 18 m/s over water when it accidentally drops a 2 kg fish. If the altitude of the bird is 5.40 meters and friction is disregarded, what is the speed of the fish when it hits the water? My work: I don't know if I did this...

Given an parachuter and the system parachuter-parachute-Earth and taking in account the resistance of the air, my question is: is the mechanical energy of the system (parachuter.parachute.Earth) a constant, please explain. And please don't talk just about the parachuter because I wan't to know...

[FONT="Arial Black"][SIZE="4"]Hi all, Homework Statement I'm stupefied. In continuation to my last thread (https://www.physicsforums.com/showthread.php?t=277124), I wanted to see if any perfectly plastic collision would make the total mechanical energy of the system go down to a factor of...

Homework Statement A 60 kg skier slides from rest down a 30 m slope that makes an angle of 26 degrees with the horizontal. Assume the coefficient of friction of the slope is .2. How much mechanical energy does the skier lose while skiing down the hill? What is the velocity of the skier...

Homework Statement A novice skier, starting from rest, slides down a frictionless 35.00 incline whose vertical height is 185 m.How fast is she going when she reaches the bottom? Homework Equations Need the rest of the solution. The Attempt at a Solution PICTURE SCAN...

Homework Statement A light inextensible string is wrapped around a cylindrical pulley of mass M that is free to rotate about its axis. The end of the string is attached to a block of mass m. Use conservation of mechanical energy to calculate the speed of the block after it has fallen a...

Homework Statement You use 556 N of constant force to push a crate 12 m horizontally across the floor, and then stop pushing, leaving the crate stopped in its new position: a) How much work did you do on the crate? b) What is the change in the total mechanical energy of the crate after being...

Homework Statement Derive the Law of Conservation of Mechanical Energy starting from the Work-Energy Theorem. State any assumptions. Homework Equations I'm not really sure where to start with this. Basically how to end up with the equation 0=\DeltaU+\DeltaK The Attempt at a Solution

Hello, Consider a system that is made of a man and a hockey ball on ice (frictionless). Say the man's mass is 80kg and the ball is 0.5kg. At t=0, they are together and they don't move. At an instant the man throw the ball at \frac{10m}{s} against a wall (the ball suffers an elastic...

1. A 1100 kg car at rest at the top of a hill accelerates down the road, reaching a speed of 20 m/s after descending a height of 120 m. What was its total change in mechanical energy (KE plus PEG) as of that moment in Megajoules? 2.KE = 1/2 mv^2 and PEg = mgh 3. I used the above...