Conservation of energy Definition and 1000 Threads

Homework Statement A roller coaster travels on a frictionless track starting at point A, 5.0m off the ground. It then comes down to point B, 0.0m off the ground (it comes down to the ground), then it goes back up to point C, at 8.0m off the ground. If the roller coaster is traveling at...

Homework Statement Two heavy balls of equal mass M are attached to the long but light metallic rod standing on the floor. The rod with the balls falls to the floor. Find the velocity of each ball at the moment when the rod hits the ground. Neglect mass of the rod and the friction between...

Homework Statement A bullet is shot into the air with muzzle veloity Vo at an angle θ with the horizontal. Use energy considerations to find a) the highest point reached and b) the magnitude of the velocity when the bullet is at half its maximum height. Homework Equations Vx = Vo*cos(θ)...

Homework Statement A particle can only move along the x axis. Forces act on it so that its potential energy function is U(x) = 1/2*k1*x^2 + 1/4*k2*x^4 where k1 and k2 are positive. The particle is started at x = a with zero velocity. a.) Where is the velocity a maximum? What is its magnitude...

Homework Statement Two rockets are launched from Earth's surface, one at 17 km/s and the other at 22 km/s. How fast is each moving when it crosses the moon's orbit? Homework Equations Kf + Uf= K0 + U0 0.5mvf^2 -GMm/R = 0.5mv0^2 - GMm/R The Attempt at a Solution So I attempted to...

I think this scenario violates the law of conservation of energy: A ball is rolling twards a fan, witch provides a constant force on the ball, with some amount of kinetic energy. As the ball gets closer to the fan, its kinetic energy is converted to "fan potential energy". Then, when the ball's...

Homework Statement https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/phys2111/fall/homework/Ch-08-GPE-ME/mass_vertical_spring/7.gif A spring with spring constant k = 45 N/m and unstretched length of L0 is attached to the ceiling. A block of mass m = 1.5 kg is...

Homework Statement The cable of an elevator of mass M = 3990 kg snaps when the elevator is a rest at one of the floors of a skyscraper. At this point the elevator is a distance d = 48.2 m above a cushioning spring whose spring constant is k = 21300 N/m. A safety device clamps the elevator...

Conservation of Energy please help! Homework Statement An 840 kg roller coaster car is launched from a giant spring of constant k=31kN/m into a frictionless loop-the-loop track of radius 6.2m, what is the minimum amount that the spring must be compressed if the car is to stay on the track...

Homework Statement Bill throws a 10.0g (0.0100kg) straight down froma height of 2.0m. The ball strikes the floor at a speed of 7.5 m/s. a) what was the original speed of the ball? b) if 30% of the balls energy is transformed in thermal energy during the collision with the floor, find the...

Homework Statement Consider the following fusion reaction 2H+3H →4He + n in which deuterium and tritium fuse together to form a stable isotope of helium plus a neutron. In all of physics, we see experimental confirmation of Conservation of Energy, in which the total amount of energy in a closed...

Homework Statement Example: A 50 kg gymnast does giant circles around a horizontal bar. At the top of her swing her center of mass is 1.0 m above the bar traveling 1.2 m/s. what is the speed of her center of mass at the bottom of her swing where her center at mass is 1.0 m below the bar? ( No...

Homework Statement A block of mass 1.5 kg is placed against a horizontal spring of force constant k that is compressed .20 m. the spring is then released and the block travels to the right along a horizontal surface. The coefficient of kinetic friction between the block and the surface is 0.4...

Homework Statement Example: A 50 kg gymnast does giant circles around a horizontal bar. At the top of her swing her center of mass is 1.0 m above the bar traveling 1.2 m/s. what is the speed of her center of mass at the bottom of her swing where her center at mass is 1.0 m below the bar? (...

Homework Statement a steel ball of m mass is fastened to light cord of length L and released when the cord is horizontal. At the bottom if its path the ball strikes a hard plastic block of mass M=4m, initially at rest on a frictionless surface. The collision is elastic. Find the speed of the...

Homework Statement A block of mass m hangs on the end of a cord and is connected to a block of mass M by a pulley arrangement. (m hangs freely, M is attached to the string, and is on a table top. (So m is attached to a string which goes therough a pulley changing the strings direction 90...

(Please make it a bit easy for a newbie student) Law of Conservation of Energy states that energy can neither be created nor be destroyed. Then how did it ever come into being? Thanks

I just want to get my head straight on something with regards to relativity and gravity - I think it's a simple question (or rather has a simple answer!) so there's no trick agenda here. If I have two bodies orbiting each other in deep space - far enough out for other gravitational forces to...

Homework Statement A child rolls a 0.600-kg basketball up a long ramp. The basketball can be considered a thin-walled, hollow sphere. When the child releases the basketball at the bottom of the ramp. it has a speed of 8.0 m/s. When the ball returns to her after rolling up the ramp and then...

Homework Statement Two blocks, of masses M = 2.1 kg and 2M are connected to a spring of spring constant k = 210 N/m that has one end fixed, as shown in the figure below. The horizontal surface and the pulley are frictionless, and the pulley has negligible mass. The blocks are released from...

Homework Statement A uniform marble rolls down a symmetric bowl, starting from rest at the top of the left side. The top of each side is a distance h above the bottom of the bowl. The left half of the bowl is rough enough to cause the marble to roll without slipping, but the right half has...

Homework Statement 2 boys of identical masses are standing on 2 identical trolleys A and B(facing each other) which are at rest on a frictionless horizontal surface.The boy on trolley A then throws a ball of mass m horizontally with velocity V with respect to the Earth and the boy o trolley B...

Hi all, There are 2 identical gears which are in the same axis. At first gear #1 rotates at angular velocity w, while gear #2 stays still. Now the gears are attached and rotate at the same angular velocity w'. Because the angular momentum is conserved so w' = 0.5 w But then the kinetic...

Take two uncharged particles (e.g., neutrons) at rest with respect to one another in empty space. Now apply 1 Joule of energy to accelerating them apart. They will eventually come again to rest with 1 Joule of gravitational potential and accelerate back together due to gravity. Their kinetic...

hi i hope some one can help me with this I'm going out of my mind with it lol. I'm new to this forum so please forgive any errors in where this thread is or if it contains something it shouldn't. a force of 160N is applied to a sliding mass of 13kg fixed on top of a spring. the spring force...

problem solved. Thanks!

Homework Statement A 1.20-kg piece of cheese is placed on a vertical spring of negligible mass and force constant k = 1800 N/m that is compressed 15.0 cm. When the spring is released, how high does the cheese rise from this initial position? (The cheese and the spring are not attached.)...

I am a tutor. I ran across this problem is a high school physics textbook. See attachment x162, my solution is on x163. I thought that mechancical energy is conserved and that loss of potential energy should be equal to gain in elastic (stored) energy. Ithink the spring constant must be wrong?

I am currently working on an experiment to find the kinetic friction in a driveline. The experiment uses the principle of conservation of energy and is based on the following experiment: http://hyperphysics.phy-astr.gsu.edu/HBASE/Class/PhSciLab/frictionex.html The difference in my proposed...

Homework Statement To make a pendulum, a 300g ball is attached to one end of a string that has a length of 1.4m and negligible mass. (The other end of the string is fixed) The ball is pulled to one side until the string makes a 30 degree angle with the vertical, then (with the string taut) the...

Hi, The first law of thermodynamics states that energy can neither be created nor destroyed. Therefore the total energy of the universe is the same in any given process. But how can the universe so be expanding ? Does its amount of energy not increase during the expansion ? I am not a...

I have devised a simple thought experiment which leads me to an absurd conclusion and I feel I’m missing something obvious but I can't see where I’m wrong and I hope you could help point out my error. I start with an empty space initially containing two masses that are at rest relative to...

Homework Statement Use conserbvation of Energy The spool has a mass of 50 kg and a raius of gratino k = .280 m. If the 20 kg block A is released from rest, determine the distance the block must fall inorder for the spool to have an angulr velocity w = 5 rad/s. Also what is the tension...

Homework Statement Solve Using Conservation of Energy The spool has a mas of 50 kg and a radius of gyration k(o) = .280m. If the 20 kg block A is released form rest, determine the distance the block must fall in order for the spool to have an angular velocity w = 5 rad/s. Also what is...

Energy cannot be created or destroyed in an isolated system. Can energy be created or destroyed in an open system? Do open systems exist? Where does energy come from? I'd appreciate it if someone could tell me more about this.

The problem is stated on the sheet i have attached along with my attempt to the possible solution. This is a proof and i am very bad at working with proofs. This seems to be a classical problem so I'm sure some of you guys might have seen it, please guide me...

Right, I'll try to get this question across. Say you have 2 bar electromagnets, aligned so when you turn them on they are attracted to each other. You start with them touching, turn them on and pull them apart. You then turn of the current and put them back together. If you continue to repeat...

When two waves that are 180 degrees out of phase interfere, the energy from both cancels out. Why is it that, for example, a sound wave, which is a form of energy, can disappear when combined with another when the Law of Conservation of Energy states that energy cannot be destroyed? I posed...

Homework Statement A roller coaster car on the frictionless track shown in the figure below starts from rest at height h. The track's valley and hill consist of circular-shaped segments of radius R. Find the formula for the maximum height h_max for the car to start so as to not fly off the...

Homework Statement A .5 kg block is dropped from 15m. A 5 gram bullet hits the block at 233 m/s. At what height must the block be hit to completely stop the blocks freefall momentarily. Homework Equations p=mv 1/2mv^2=mgh The Attempt at a Solution bullets ke...

Homework Statement An open container of mass 50.0 kg is rolling to the left at speed of 5.0 m/s on a frictionless surface. A 15.0 kg box slides down a 37° inclined plane and leaves the end of the plane with speed of 3.0 m/s. The end of the plane is a vertical distance of 4.0 m above the...

Homework Statement Homework Equations Wgravity = mgh KE=1/2mv2 The Attempt at a Solution I know the gravitational potential energy is different because mgh accounts for mass. But the book says that B is correct. I don't know why because isn't the less mass you have the faster you go? 2KE/m=v2

When current is introduced inside of a wire it creates a magnetic field...also generating a magnetic potential energy for any nearby magnetic fields. How is energy conserved in this process? Similarly... I read that a large 13 mile wire was put into orbit around Earth's magnetic field...

Homework Statement A 179 g block is launched by compressing a spring of constant k=200 N/m a distance of 15 cm. The spring is mounted horizontally, and the surface directly under it is frictionless. But beyond the equilibrium position of the spring end, the surface has coefficient of friction...

Homework Statement A loaded 305kg toboggan is traveling on smooth horizontal snow at 4.60m/s when it suddenly comes to a rough region. The region is 9.00m long and reduces the toboggan's speed by 1.10m/s. Homework Equations What average friction force did the rough region exert on the...

Homework Statement A 79 kg skier leaves the end of a ski-jump ramp with a velocity of 26 m/s directed 25° above the horizontal. Suppose that as a result of air drag the skier returns to the ground with a speed of 24 m/s, landing 18 m vertically below the end of the ramp. From the launch to...

Homework Statement A 1.90 g ice flake is released from the ege of a hemispherical bwon whose radius r is 28.0 cm. The flake bowl contact is frictionless. What is the speed of the flake when it reaches the bottom of the bowl. Homework Equations I took KINETIC ENERGY = GRAVITATIONAL...

Homework Statement The ball launcher in a pinbgall machine has a spring that has a force constant of 36 N/cm. THe surface on which the ball moves is inclined theta=10.1 degrees with respect to the horizontal. If the spring is initially conressed 4.25 cm, find the launching speed of a .120 kg...

Homework Statement A 70.4 kg man steps out of a window and falls (from rest) 1.33 m to a sidewalk. at is his speed just before his feet stke the pavement? If the man falls with his knees and ankles locked, the only cushin for his fall is a 0.508 cm give in the pads of his feet. Calculate...

Homework Statement A 54.2 kg student climbs a 6.95 m rope and stops at the top. What must her average speede in order to match the power output of a 110 W lightbulb? Homework Equations PE=mgh KE=1/2mv^2 W=(Xf-Xi)(cos theta)(F) W= delta KE PE+KE = PE+KE (before and after) The Attempt...