Mechanical energy Definition and 358 Threads

How can kinetic or mechanical energy be stored?

Homework Statement A particle of mass m moves along the x–axis under the influence of force ##F_x=-ax+bx^3## , where a and b are known positive constants. (a) Find, and sketch, the particle's potential energy, taking U(0) = 0 (b) Identify and classify all equilibrium points (c) Find the...

Homework Statement A force F acts over the block as show in the figure. F have a constant magnitude, but has a variable direction. The direction of F, at any given instant, always is directed to the point P. Evaluate the work done by the force F through the displacement d between the points R...

Homework Statement A block of mass ## m ##, attached to a rope, is dropped at the point A. When the block reaches the point B, the tension is ## T = 2 \cdot m \cdot g ## and the rope broke at that same point. If the length of the rope is ## L = 6cm ##, evaluate the height ## h ## where the...

How do conservative forces exactly conserve mechanical energy while non conservative forces do not. Also why is potential energy defined only for conservative forces?

I think I miss something about energy of a mechanical wave. In absence of dissipation the mechanical energy transported by an harmonic wave is constant. $$E=\frac{1}{2} A^2 \omega^2 m$$ But, while studying normal modes on a rope, I find that the mechanical energy of a normal mode (still...

I'm confused about energy driven by a wave. Consider a sinousoidal wave moving in a rope. Each element ##dm## of the rope follows a simple harmonic motion in time. That means that the mechanical energy ##dE=dK+dU## of the element ##dm## is constant. Nevertheless on Halliday-Resnik-Krane I...

MENTOR Note: Thread moved here from Classical Physics hence no template I have a question set that I need to be able to answer before my exam next month, I know how to answer all of them except this one. I get the feeling I'm being an idiot. Show that the simple harmonic motion solution of the...

Homework Statement The right answer is E, and I have no idea how to solve this problem. Please advise on how to proceed. Thanks in advance. Homework Equations conservation of mechanical energy?? The Attempt at a Solution Many attempts were done, but I am lacking on theory with this. How...

This isn't about a specific physics problem, but rather a question: Given I have a ball or cylinder rolling smoothly along some path, is it generally true that mechanical energy is conserved? I.e. if ##E_mech = K+U = K_{trans} + K_{rot} + U##, then ##\Delta E_mech = 0##? I have been able to...

I'm studying effective potential in Newtonian gravitation. The mechanical energy of a body can be written $$E=\frac{1}{2}\mu {\dot{r}}^2+\frac{L^2}{2\mu r^2}-\gamma \frac{m M}{r^2} \tag{1}$$ Where \mu is the reduced mass of the system planet-star. Consider now the term...

Homework Statement If two objects of unequal mass and unequal Kinetic energy hit each other, they lose some energy to other forms but keep enough to do Work on each other. A good example is a car and wind, a man and ball could also apply, a ball with KE could stop a running man if KE does work...

Hello Forum, Conservation of mechanical energy ME= KE+PE happens when the net work done by the non conservative forces is zero. Conservation of total momentum, instead, happens when the external net force is zero (or close to zero). In the case of mechanical energy, the non-conservative forces...

Homework Statement An 80-N box is pulled 20m up a 30 degree incline by an applied force of 115 N that points upward, parallel to the incline. If the coefficient of kinetic friction between box and incline is 0.22, calculate the change in the kinetic energy of the box. Homework Equations ΔKE =...

Im sure Imma mess this up, probably because I am really tired...but I have a bullet that weights .015kg's and is moving at 285m/s, so 609.18J's as with KE. I hit a 70kg block, penetrates .3048 meters thus exerting 1998.62N's of force, which is a lot of force. .3048/285m/s so 0.00106 seconds...

Hi, Could you please help me determine if I've worked this problem out correctly. 1. Homework Statement A 2.86-kg object on a frictionless horizontal surface oscillates at the end of a spring with an amplitude of 7.81 cm. Its maximum acceleration is 3.74 m/s2. Calculate the total...

Homework Statement A mass ##m_1 = 5.0 kg## is hanging from the end of a thread, of negligible mass, that slides on a pulley, of negligible mass too and without friction. At the other end of the thread, at the same height of ##m_1##, there is another hanging mass ##m_2 = 3.5 kg##. Using the Law...

Homework Statement This is from an exam for my current course in "Mechanics 2", from a couple of years ago, which means that the correct answers are given for checking results, but without further explanations. I'm confused about part (c) where my results do not correspond with the given...

Homework Statement I have been tasked with showing "how the mechanical energy of a planet determines the shape of its orbit", and I cannot for the life of me make sense of it. I've run into a formula, see below, but I'm not sure how to interpret it nor if it even applies in my case at all (as E...

Hi I'm really at a loss: How should this formula be interpreted? Is e simply dependent on the specific mechanical energy of, say, a planet in orbit around the Sun as well as its angular momentum?

Homework Statement Find the horizontal distance the skier travels before coming to rest if the incline also has a coefficient of kinetic friction equal to 0.210. Assume that theta = 20.0°. Homework EquationsThe Attempt at a Solution

Homework Statement Attached figrue shows an 8.00 kg stone at rest on a spring.The spring is compressed 10.0 cm by the stone. (a) What is the spring constant? (b) The stone is pushed down an additional 30.0 cm and released.What is the elastic potential energy of the compressed spring just...

Hi, I've been trying to figure out how to solve this problem for a few hours, but whatever I do it seems to give me the wrong answer. Problem statement: Fetch data from the roller coaster model. Ignore friction. What is the mechanical energy in cart in situation 1? ## E = E_k + E_p ## Which...

Homework Statement I did an experiment in which I bounced a ball under a motion sensor. From that I got a generated graph on the computer in the shape of a parabola. The max height of the ball at each interval was also obtained from looking at the graph. From the maximum height values, I...

Homework Statement At a certain location, wind is blowing steadily at 10m/s . Determine the mechanical energy of air per unit mass and the power generation potential of a wind turbine with 60m diameter blades at the location. Density of air is 1.25kgm-3. ( ans : 0.05kJ/kg, 1770kW ) Homework...

Hi, I was woking on a problem from Taylor Mechanics.(4.27) It reads: Suppose that the force F(r , t) depends on the time t but stillsatisfies ∇ × F = 0. It is a mathematical fact that the work integral ∫12F(r , t) ⋅ dr (evaluated at anyone time t) is independent of the path taken between the...

I got a little bit confused while studying gravitational potential energy, particularly the expression for long distances: (-GMm/r). An exercise asks me for the velocity, period and radial acceleration for a 1000kg satellite that I wish to put into orbit. That's okay. But after that, I'm...

Homework Statement Homework EquationsThe Attempt at a Solution Suppose the free end of hte spring moves towards right .Consider a reference frame moving with speed 'v' along with the free end of the spring . From this frame ,the block has an initial speed 'v' towards left . At maximum...

Homework Statement A simple harmonic oscillator consists of a block of mass 45 g attached to a spring of spring constant 240 N/m, oscillating on a frictionless surface. If the block is displaced 3.5 cm from its equilibrium position and released with an initial velocity of 2.5 m/s, what is its...

Homework Statement An "energy bar" contains 22 g of carbohydrates. If the energy bar was his only fuel, how far could a 68 kg person walk at 5 km/h? Mass(person) = 68 kg; v = 5km/h; 22g carb = 4 Cal/1 carb = 88 Cal; P(power of man walking) = 380W (this is derived from my textbook). Homework...

Homework Statement This is my first time posting here guys so correct me if I am wrong. This question was on my test and I wanted to know if I did it right. There is a block of mass m and it is moving at a certain velocity before pressing against a spring which compresses distance x. Find...

Homework Statement Homework EquationsThe Attempt at a Solution So for part a, i just plugged 3 into the equation, got the U(3) = -5.36 to get mechanical energy, (KE + PE): 5 J + (-5.36 J)= -0.36 J is this correct? what does it mean when the total energy is a negative value? (I have never...

I am a little confused about how mechanical energy conservation operates when it comes to things like predicting velocity. I know that if conservative forces are the only forces acting on a body, then we can say that mechanical energy is conserved. This is simple to see when we have lateral up...

First of all, I did not major in Physics, but I did pass GCE with A. (This is to make a point, not to boast.) But there's a matter that doesn't make any sense to me, and none of my acquaintances could give me the clarification so I came to this forum, hoping someone can make me understand this...

Homework Statement You do 100 J of work while pulling a child back on a swing, whose chain is 2.0 m long, until the swing makes an angle of 30.0° with the vertical. a) What is the child's mass? (Consider the swing itself and the chain massless) b) Upon releasing the swing from this position...

Is there an optimum number of washers to be used on a threaded bolt in respect to dissipation of energy towards the nut? And how would one calculate the dissipation rate of each washer?

Homework Statement In the system shown, the block M (mass of 15.65 kg) is initially moving to the left with a speed of 3.4 m/s The mass of m is 8.26 kg and the coefficients of friction are μs=0.411 and μk=0.304. The string is massless and the pulley is massless and frictionless. How fast will M...

Homework Statement A roller coaster at an amusement park is at rest on top of a 30 m hill (point A). The car starts to roll down the hill and reaches point B which is 10 m above the ground, and then rolls up the track to point C, which is 20 m above the ground. (A) A student assumes no energy...

An Object slides with a consistent velocity down an incline that has a 30 degree angle. I'm trying to find the kinetic friction and the ratio that the mechanical energy is lost on the way down. I think I have already calculated µ with F(friction)= µmgcos(θ)=mgsin(θ) out comes Tan(θ) = µ I...

We want to slide a 12-kg crate up a 2.5-m-long ramp inclined at . A worker, ignoring friction, calculates that he can do this by giving it an initial speed of 5 m/s at the bottom and letting it go. But friction is not negligible; the crate slides only 1.6m up the ramp, stops, and slides back...

Tim drops his watch from a 3-story-building, 12.5 m above ground. In task a. you were asked to find what the v was when it hit the ground, the answer was 15.7. However I am having trouble finding the answer to task b in which you are asked to find the h when the watch is dropped at the speed of...

What are the conditions necessary for applying the conservation of mechanical energy or the conservation of momentum? Can we apply these anywhere or do we require specific conditions which have to be fulfilled for applying them?

So I am awere of everything in electromagnetism in physics,but lately I am enjoying in creating RC cars.But I only got to making a car going only forward,how can i make him turn?How could I transform only a part of the electrical energy into mechanical so that my RC car can turn left and right...

When one lifts a block off of the ground and holds it in the air, the work done by one's lifting force is equal to the change in total mechanical energy of the block/earth system. Since the mechanical energy is KE+PE and since KE doesn't change during the motion, the work done by the lifting...

Homework Statement A 20.0 kg cannonball is fired from a cannon with a muzzle speed of 1000 m/s at an angle of 37.0° with the horizontal. A second ball is fired at an angle of 90.0°. (a) Use the isolated system model to find the maximum height reached by each ball. (b) What is the total...

Homework Statement A block with mass m rests on a smooth, frictionless ramp with mass M and height h. The ramp itself sits on a frictionless horizontal surface in which it is free to slide. The block slides smoothly down the ramp from rest. We want to find the speed of the block after it has...

When do one use the principle of conservation of mechanical energy to find the velocity of a mass, and when would you use the sum of forces equals to the mass times acceleration, and there after use a ds=v dv in order to find the velocity. The specific question related to this is a spring fixed...

Homework Statement A 5.0 kg block hangs from a spring with spring constant 2000N/m. The block is pulled down 5 cm from equilibrium position and given an initial velocity of 1.0 m/s back toward equilibrium. What are the a.) frequency b.) amplitude c.) total mechanical energy of the motion...

At the moment when a shot putter releases a 5.00 kg shot, the shot is 2.00 m above the ground and traveling at 15.0 m/s. It reaches a maximum height of 8.00 m above the ground and then falls to the ground. Assume that air resistance is negligible. a. What was the potential energy of the...

Homework Statement a 6-kg bullet is fired into a 2-kg block initially at rest at the edge of a table of height 1 m. The bullet remains in the block, and after the impact the block lands 2 m from the bottom of the table. Determine the initial speed of the bullet. Homework Equations m1v1i...