Mechanical energy Definition and 354 Threads

Homework Statement a) Write down the steady-state mechanical energy equation for flow from point (1) (located at the free surface of the creek) to point (2) located at the free surface of the tank. For the purposes of this problem you can assume the pressures at both points are atmospheric...

Hi everyone , this exercise was given in one of my midterms , but we didn't correct it and I'm wondering where I went wrong on it : Help will be extremely appreciated : Here is the statement : A block of mass m=2 kg is pushed by a spring with a spring constant of k=650 N/m which is...

Problem: the masses of the javelin, discus, and shot are .8 kg, 2.0 kg, and 7.2 kg, respectively, and record throws in the track events using these objects are about 89 m, 69 m, and 21 m, respectively. Neglecting air resistance, (a) calculate the minimum initial kinetic energies that would...

Mechanical energy is conserved whenever momentum is conserved. T/F? My guess is true: If momentum is conserved, no external forces are applied on the system. Hence mechanical energy can't change! (No change in PE, no change in KE). BUT: My answer booklet says FALSE! Why?

A box containing a pebble is attached to an ideal horizontal spring and is oscillating on a friction-free air table. When the box has reached its maximum distance from the equilibrium point, the pebble is suddenly lifted out vertically without disturbing the box. Will the following...

Homework Statement A damped mass-spring system oscillates at 285 Hz. The time constant of the system is 8.8 s. At t = 0 the amplitude of oscillation is 1.3 cm and the energy of the oscillating system is 36 J. Part 1: What is the amplitude of oscillation at t = 8.7 s? Answer in units of...

1. Find an expression for the total mechanical energy when the string is extended and find the maximum distance that the particle falls in terms of g Unsure 3. My attempt at solutionHi :-p Here is the question I am looking at http://imgur.com/a6T8zH7I take the datum as the fixed point so...

Homework Statement A block of mass 2.5 kg is placed against a compressed spring (k = 2900 N/m) at the bottom of an inclined plane (angle = 28 degrees). When the spring is released the block is projected up the incline and the spring expands by 14 cm to its normal length. a.Calculate the...

Homework Statement Question in entirety: Vladimir Putin has contacted you to redesign the ski jump at the Olympic games. In the ski jump, contestants begin at rest at the starting gate on top of a hill inclined at an angle of 30 with respect to horizontal. They then accelerate down the hill...

Is momentum conserved when it is said that the mechanical energy is? My teacher says no, but I cannot think of any example. Looking at the formulas, it seems as though constant mechanical energy will always conserve momentum...

Object with positive mechanical energy in an attractive force field moves along a hyperbolic path and whose energy is zero, moves along parabolic path...isn't it?...But why?...Can't any object with ve energy move along the line joining centre of force?...If its radial component of kinetic...

Homework Statement A wooden block is on an incline with θ = 18.5 degrees. The angle was determined to be big enough that the wooden block would experience kinetic friction ( slides down the ramp). A photo-gate was used to measure the time it took for the block to move a certain distance. Five...

Homework Statement What is the total mechanical energy of a 290 kg satellite in a geosynchronous orbit around the Earth? Homework Equations W= K + UG where K= 1/2 (mv2) and UG= -(GmM)/r Fc= mac where ac= v2/r The Attempt at a Solution I think the geosynchronous part is what is...

Homework Statement What is the total mechanical energy of a 380kg satellite in a circular orbit 3.0 Earth radii above the surface? Homework Equations W= E2- E1 E= 1/2 mv2- \frac{GmM}{r} The Attempt at a Solution I'm not sure if the equations above are suitable to solve this or...

1. Homework Statement [/b] A car is rolling down a ramp that is inclined at and angle of 9.9 degree with respect to horizontal. There is no friction acting from the road on the tires. Employ conservation of mechanical energy to find the speed of a car that starts from rest and rolls down...

Homework Statement What's the total mechanical energy of a 400kg satellite in circular orbit 1100km above Earth's surface? Homework Equations The Gravitational potential energy U=-(Gm1m2)/r kinetic energy k=1/2mv^2 The Attempt at a Solution At first i thought i could do...

Homework Statement Converting the energy of one food calorie into mechanical energy, starting from rest, to what speed could you accelerate a 133-lbs person? Homework Equations 1 calorie= 4.184J 1 lbs= 0.453592kg K=1/2mv^2 The Attempt at a Solution here what I did, I converted the...

Homework Statement When a .5kg mass is suspended from a spring, the spring stretches 4cm. The mass is then displaced 2cm from its equilibrium position and released. (a) What is the spring constant? (b) What is the mechanical energy of the mass? (c) What is the speed of the mass as it passes...

Homework Statement A 58.5 kg child slides down a water slide with a velocity of 1.2 m/sec at the top. At the bottom of the slide, she is moving horizontally, y=1.5 meters above the water. She splashes into the water d=2 meters to the left of the bottom of the slide. 1) Assuming potential...

Homework Statement Using the equation for the final velocity of an inelastic collision, show that mechanical energy is not conserved in the collision. (Do this only with variables.)Homework Equations Vf = (m1v1i + m2v2i)/(m1 + m2) KE = (1/2)mv2 TME = KE + PEThe Attempt at a Solution I honestly...

What is the total mechanical energy (self energy) of the universe that is due to the fact that it expands, taken the big bang as the origin - on the basis of general relativity? If anyone could supply me with the equation and number (what size is it in kgm2/s2) I would be very thankful.

In griffith it is mentioned that the sum of the mechanical energy and electromagnetic field energy are conserved in a system, how is the mechanical energy defined in this case since a potential energy cannot be defined? Is it just the kinetic term by itself?

Homework Statement A spring cannon is used to shot horizontally a marble mall, whose mass is 75g, from a platform located 1.2 m from the ground. If the spring compression is 25 mm, the ball hits the ground 4,2m from the base of the platform. Not taking friction into account, determine...

Homework Statement A point charge q1=5μC is held fixed in space. From a horizontal distance of 6.00 cm, a small sphere with mass 4g and charge 2μC is fired toward the fixed charge with an initial speed of 40.0 m/s. Gravity can be neglected. What is the acceleration of the sphere at the...

Homework Statement A skier of mass m starts from rest at the top of a solid sphere of radius r and slides down its frictionless surface. At what angle θ will the skier leave the sphere? Homework Equations KE= 0.5mv^2 PE = mgh Fc = (mv^2)/r The Attempt at a Solution I am really...

Homework Statement A 1.2 kg dynamics cart is rolling to the right along a horizontal lab desk at 3.6 m/s, when it collides head on with a spring bumper that has a spring constant of 2.00 * 10^2 N/m. a) Determine the maximum compression of the spring b) Determine the speed of the cart at...

Hey guys, I'm trying to complete a homework problem, but I'm not quite sure how to approach it. Here is the question: A 90.5-kg fullback running east with a speed of 4.91 m/s is tackled by a 94.7-kg opponent running north with a speed of 2.93 m/s. Determine the mechanical energy that...

I have a quick question: does a block that has initial velocity from start have any potential energy on a flat surface (not on an angle or anything just a flat horizontal surface) ? I was thinking no because it has no energy stored and all of it is kinetic, because it is in motion?

Homework Statement A 65 kg man goes for a 72 minute hike up a mountain that is 400.0 metres in vertical height. The energy consumption rate for this climb is 10.1 kcal/min. What is the Mechanical Energy (useful work energy) expended for this hike? (in kcal) Homework Equations ME=...

Homework Statement Which of the following statements is/are true? Choose all that apply. a. The total mechanical energy of a system, at anyone instant, is either all kinetic or all potential energy. b. The total mechanical energy of a system is equally divided between kinetic and...

Regarding momentum, and the "Law of conservation of linear momentum", my book states that it's more general than mechanical energy, since mechanical energy is only conserved for conservative forces, while linear momentum is conserved independent of the forces, as long as the sum of external...

Homework Statement A sphere rolls from rest down a slope without slipping. Show using energy considerations that the speed of the sphere once it reaches the bottom is V = \sqrt{\frac{10gh}{7}} Homework Equations mgh = \frac{1}{2}mv^{2} + \frac{1}{2}Iw^{2} The Attempt at a Solution...

Homework Statement A .420kg ball is throw vertically upward at an intial sped o 12.1 m/s. If the initial potential energy is taken as zero find the bal's kinetic, potential, and mecanical energies a.) at its intial position b.) at 1.75m above the initial position, and c.) at its maximum...

A 75g Frisbee I thrown from a point 1.1 m above the ground with a speed 12 m/s when it has reached a height $.1 m its speed is 10.5 m/s What is the reduction in Emec of the frisbee-earth system because of air drag? At first I thought Since ΔEmec= Δk+Δu the change is -0.61 J Then I...

Homework Statement what would be the total mechanical energy of a 200 kg satellite in a geosynchronous orbit around the earth? The only known data is the radius of the Earth and mass of the Earth the mass of the satellite, m=200 kg, it would have a period of T=24h, but i do not know the radius...

Homework Statement a)Suppose the chancellor of the university drops a 2.00 kg water balloon from the administration building balcony 10.0 m above the ground. The chancellor takes the origin of his vertical axis to be even with the balcony. A student standing on the ground below the...

Hello, i was wondering if someone can help me out. I finished law of momentum, and learned that for the conservation of momentum to be applicable, the system must be isolated. An isolated system means no external forces, correct? if i am correct, then i don't understand the law of...

A cyclist has a speed of 5 m/s when she beings to coast down a hill, as shown in the figure. At the bottom of the hill, her speed has increased to 12m/s. the mass of the cyclist plus bicycle is 75kg. a) Calculate the work done by gravity on the cyclist and bicycle. b) Calculate the...

1. A 750-kg automobile is moving at 20.0 m/s at a height of 5.0 m above the bottom of a hill when it runs out of gasoline. The car coasts down the hill and then continues coasting up the other side until it comes to rest. Ignoring frictional forces and air resistance, what is the value of...

Homework Statement Ok, this really IS my last question here. Again, I have a fairly close answer that isn't right. A 1630-kg communications satellite is released from a space shuttle to initially orbit the Earth at a radius of 9. 106 m. After being deployed, the satellite's rockets...

Homework Statement A 250 gram mass is connected to a spring and executes simple harmonic motion. The period of motion is 0.5 seconds and the total mechanical energy is 0.50J. What is the amplitude of motion? Homework Equations ΔU = 1/2kx2 The Attempt at a Solution I get 1/2kx2 =...

Hey, I was trying to prove to myself an expression for the total energy, and I got stuck Here is the picture (it's transparent, so I won't embed it here). The problem I seem to be having is when I observe these two points where the speed is in its highest and its lowest. Since in these...

Hello world. Is there any way to convert mechanical energy into DC electricity energy WITHOUT using any magnets ? I know there is homopolar generator but it uses magnet and as I said I need something that doesn't use any magnets. I also know there are stuff that use friction (triboelectric...

So I know that the total mechanical energy is E=0.5m*v^2+ 0.5* k*x^2 But sometime I see it written as E=0.5m*v^2+ 0.5* k*A^2 What is the difference? Here is a question If the amplitutide of the oscillations is doubled the mechanical energy of the system: Doubles Does not change...

Ballistic Pendulum system. Bullet weighs .00500kg and the wooden block it hits weighs 1.00kg. The increase in height is .05m. Using conservation of momentum and conservation of energy I have calculated the bullets speed at 199m/s. How can I calculate the loss in mechanical energy as a result...

I am trying to consolidate my understanding of kinematics and mechanics. If there is no such thing as friction, and the only force in the universe is gravity, then can we prove using the laws of kinematics and the definition of potential energy/kinetic energy that the mechanical energy of...

Conservation of Mechanical Energy and Momentum in total inelastic collisions? In an inelastic collision, such as a bullet getting stuck in a block hanging on a string, has two types of conservations? -Total Inelastic Collisision Conservations: (1) Conservation of Mechanical Energy: Uo+Po =...

Hi, I was just wondering, is mechanical energy conserved when two cars of equal mass and moving at equal speed collide head-on and in the process both come to rest? I'm inclined to say it isn't conserved because kinetic energy is converted into other forms of energy (e.g. heat and sound)...

Hey guys, I have a test tomorrow in physics and although I'm a good student, physics is getting tougher this year (high school 1st year for me) and our teacher is really bad, her teaching skills are very poor. Plus, I've been absent for a couple of days when we had physics and I can't solve the...

Homework Statement A 30g bullet is moving at a horizontal velocity of 500m/s come to a stop 12 cm within a solid wall. What is the change in mechanical energy of the bullet? Homework Equations Mechanical energy = 1/2mv^2+mgh The Attempt at a Solution The question is for 6...