Conservation of energy Definition and 1000 Threads

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...

Homework Statement A 2.5 kg block of ice at a temperature of zero degrees celcius and an initial speed of 5.7 m/s slides across a level floor. If 3.3 x 105 J are required to melt 1 kg of ice, how much ice melts, assuming that the initial kinetic energy of the ice block is entirely converted to...

Could some one please explain to me why energy is conserved in a roller coaster car on a frictionless roller coaster car ride when the conservation law says that energy will only be conserved when their are no outside forces applied. Isnt the force supplied by the rails to change the cars...

Homework Statement Show that on a roller coaster with a circular vertical loop, the difference in your apparent weight at the top of the circular loop and the bottom of the loop is 6 g's--that is six times your weight. Ignore friction. Show also that as long as your speed is above the minimum...

Hmm. This is another thing I'm unsure abt. When some mechanical energy is converted to internal energy, can we still say that energy is conserved? Can the internal energy be negative? Thanks for answering my qns :)

Homework Statement A 0.570-{\rm kg} wood block is firmly attached to a very light horizontal spring(k=180 N/m). It is noted that the block-spring system, when compressed 4.4 cm and released, stretches out 1.7 cm beyond the equilibrium position before stopping and turning back. What is the...

Two snow-covered peaks at elevations of 3500 m and 3400 m are separated by a valley. A ski-run having a total length of 3000 m extends from the top of the higher peak to the top of the lower one. A skier starts from rest on the higher peak. With what speed will the skier arrive at the topof...

[b]1. A bowling ball is hanging by a wire from the ceiling, and is swinging back and forth... [b]2. At what position(s) does it have the least speed?, greatest speed?, least kinetic energy and why?, greatest kinetic energy and why?, greatest mechanical energy and why? The Attempt...

Homework Statement The cable of the 1800 kg elevator in Figure 8-56 snaps when the elevator is at rest at the first floor, where the cab bottom is a distance d = 3.7 m above a cushioning spring whose spring constant is k = 0.15 MN/m. A safety device clamps the elevator against guide rails so...

Homework Statement A pendulum consists of a 4.0 kg stone swinging on a 3.2 m string of negligible mass. The stone has a speed of 7.7 m/s when it passes its lowest point. Homework Equations (a) What is the speed when the string is at 62° to the vertical? (b) What is the greatest angle with...

A cart, initially at rest, slides down a frictionless ramp onto a horizontal frictionless surface which is a distance h below the original position of the cart. It then collides with the free end of a relaxed horizontal spring, the other end of which is fixed to a wall. As a result the spring...

Homework Statement A parachutist with mass m = 70 kg jumps from an airplane traveling at a speed v = 100 km/h at a height H = 2500 m and lands with a speed vf = 5.00 m/s. Use the “conservation of energy strategy” to calculate the change in internal energy of the system from just after the...

Homework Statement A 75.0 kg mass sits on an inclined plane, and a rope passing over a pulley at the top connects it to a hanging 125 kg mass. The pulley is frictionless and its mass is negligible. The coefficient of friction between the 75.0 kg block and the plane is 0.143. The system is...

Alright, so I'm a little stuck on the last bit of this problem: The cable of the 1,800 kg elevator cab snaps when the cab is at rest at the first floor, where the cab bottom is a distance d = 3.7 m above a cushioning spring whose spring constant is k = 0.15 MN/m. A safety device clamps the cab...

Homework Statement why is the gravitational potential energy of a ball equal to its kinetic energy Homework Equations KE=PE The Attempt at a Solution im really not sure, i think its because energy is conserved but i don't know why that is either

Homework Statement How does a roller coaster demonstrate the law of conservation of energy by the transfer of potential energy to kinetic energy Homework Equations KE=PE The Attempt at a Solution i believe that as the roller coaster descends down the hill the potential energy...

Homework Statement a moving train collides with a train that is not moving, and the trains use their springy bumpers to bounce off of each other without damage. Assume diff masses for train A and B. Identify your isolated system, solve for the final velocity of EACH train in terms of INITIAL...

Homework Statement The sliding block has a mass of 0.800 kg, the counterweight has a mass of 0.460 kg, and the pulley is a hollow cylinder with a mass of 0.350 kg, an inner radius of 0.020 m, and an outer radius of 0.030 m. The coefficient of kinetic friction between the block and the...

Homework Statement An alpha particle with kinetic energy 10.5 MeV makes a collision with lead nucleus, but it is not "aimed" at the center of the lead nucleus, and has an initial nonzero angular momentum (with respect to the stationary lead nucleus) of magnitude L = p_0 b, where p_0 is the...

Homework Statement Homework Equations Rotational Kinetic Energy = 1/2*I*w^2 The Attempt at a Solution I was just wondering if someone explain to me why the potential energy is MgL/2 ? Is this not the same for the torque from gravity?

Homework Statement A climber's gravitational potential energy increases from 14000 J to 21 000 J while climbing a cliff. She expends 18 000 J of energy during this activity. What is the efficiency of this process? Homework Equations Efficiency= useful output/ total input Total...

Conservation of Energy Problem: Where did it go?? Imagine I shoot a boulder vertically into the air with a massive cannon. Its kinetic energy is converted into gravitational potential, and into KE of air particles (air resistance). So at m metres above the ground, mgh is the Potential energy...

Homework Statement A skier of mass 55.0 kg slides down a slope 11.7 m long, inclined at an angle θ to the horizontal. The magnitude of kinetic friction is 41.5 N. The skier's initial speed is 65.7 cm/s (0.657 m/s) and the speed at the bottom of the slope is 7.19 m/s. Determine the angle θ from...

Hi everybody! So this is my first time using this forum. I'm currently taking AP Physics C: Mechanics in high school and I have some questions concerning Potential Energy and Conservation of Energy. Thanks for taking the time to help me! Homework Statement 32. A 4.0-lb block slides...

Homework Statement A particle sits at the top of a sphere of fixed radius a. It is given a tiny nudge and begins to slide down the frictionless surface of the sphere. My attachment won't work so I'll try and explain. Theta, \theta, is the angle which the particle makes with the vertical axis...

Homework Statement An atom of mass M is initially at rest, in its ground state. A moving (nonrelativistic) electron of mass m_e collides with the atom. The atom+electron system can exist in an excited state in which the electron is absorbed into the atom. The excited state has an extra...

Homework Statement 1. A block mass m is pushed up against a spring, compressing it a distance x, and the block is then released. The spring projects the block along a frictionless horizontal surface, giving the block a speed v. The same spring projects a second block of mass 4m, giving it a...

Homework Statement A red car and a blue car collide at an in intersection. Prior to the collision the red car with mass 1000kg was heading North at 15m/s. The blue car with mass 1500 kg was heading East at 20m/s. The collision is completely inelastic with the cars sticking together and...

1. Tarzan and Jane, whose total mass is 115.0 kg, start their swing on a 5.0 m long vine when the vine is at an angle of 30.0° with the horizontal. At the bottom of the arc, Jane, whose mass is 50.0 kg, releases the vine. What is the maximum height at which Tarzan can land on a branch after his...

Dear All, Suppose we have a movable inclined plane (initially at rest) which has height h (if we attach wheels, then it should be movable) and assume that there is no friction anywhere. If a block travels with speed V towards the plane and goes up to the distance h, I wonder ; Is mechanical...

Homework Statement "Show how conservation of energy (with only gravitational potential energy and kinetic energy) can be gotten from Newton's Laws. This was the question that was asked of me, and sorry for the wording not being terribly precise. Homework Equations I am not exactly...

Homework Statement A man lifted a full keg of beer (mas 62kg) to a height of about 2m 676 times in 6 hours. Assuming that work was done only as the keg was going up, estimate how many such kegs of beer he would have to drink to reimburse his energy expenditure. (1 L of beer is approximately...

During a rockslide, a 340 kg rock slides from rest down a hillside that is 500 m long and 300 m high. The coefficient of kinetic friction between the rock and the hill surface is 0.24. (a) If the gravitational potential energy U of the rock-Earth system is set to zero at the bottom of the...

Homework Statement 1. A roller coaster car of mass 1500kg starts a distance H =23m above the bottom of a lopp 15m in diameter. If friction is negligible, the downward force of the rails on the car when it is upside down at the top of the loop is ? 2. Lou is trying to kill mice by swinging a...

A 28 kg bear slides, from rest, 6 m down a lodgepole pine tree, moving with a speed of 5.9 m/s just before hitting the ground. (a) What change occurs in the gravitational potential energy of the bear-Earth system during the slide? (b) What is the kinetic energy of the bear just before...

Homework Statement A child's toy consists of a block that attaches to a table with a suction cup, a spring connected to that block, a ball, and a launching ramp. The spring has a spring constant k, the ball has a mass m, and the ramp rises a height y above the table, the surface of which is...

Homework Statement A roller coaster car has a mass of 800kg. It is released from the top of the hill A and moves without friction down the track. Determine the minimum exit velocity vD at ground level so that the car travels around both the circular loops (Loop B - Radius= 10m, Loop C -...

Homework Statement Two stones are thrown with the same initial speed at the same instant from the roof of a building. One stone is thrown at an angle of 30 degree above the horizontal; the other is thrown horizontally.(Neglect air resistance.), which of the following is true: (a)The...

Homework Statement A cylinder is released from rest from the top of an incline of inclination 'n' and length "L". If the cylinder rolls without slipping what will be its speed at the bottom?The Attempt at a Solution This is an example question from my textbook! The solution has been given. It...

Homework Statement A 2300g mass starts from rest and slides a distance L down a frictionless 26 degree incline, where it contacts an unstressed 34cm long spring of negligible mass as shown in the figure. The mass slides an additional 17cm as it is brought momentarily to rest by compressing the...

Homework Statement A 6kg block slides on a horizontal frictionless surface with a speed of 1.2 m/s. It is brought momentarily to rest when it hits a bumper that compresses a spring. Heres a picture of the problem. When I was doing this problem, I thought there were only two different...