problem#1 Terry and Jolon are enjoying their physics class, and want to learn mo

Question

problem#1 Terry and Jolon are enjoying their physics class, and want to learn more about work and energy. They decide to stay after class to discuss the topics and see whether they can gain a better understanding. They use this simulation to help them. The system in this simulation consists of the block and the spring. In the simulation, the friends should assume that the surface is level and frictionless. They can use the mouse to move the block and compress the spring, then let the block go to release it. They should note that the energy diagram shows the kinetic, potential, and total mechanical energies of the block–spring system.

Problem#2 Joanna and Pedro are organizing a physics-themed party to celebrate everyone in their physics class passing the recent midterm examination. One planned activity is throwing water-filled balloons from the top of the physics building to the ground below, where a big target will be painted on the sidewalk.

The friends are very curious about the energy and behavior of the thrown water balloons. They wonder whether the launch angle makes a difference in how long it will take for a balloon to hit the ground, and whether changing the angle makes a difference in its speed just before impact.

In this simulation, they can explore the final speed of identical balls thrown with the same initial speed but at different release angles (and, consequently, different initial velocity components) from the top of a building. They'll use the slider to adjust the release angle for the ball. They can compare the flight paths of balls thrown at various angles, and click "clear" to erase all previous paths and start over. The graph at the top right of the simulation shows the kinetic energy, gravitational potential energy, and total energy of the ball-Earth system (ignoring frictional effects; consider the ball to be a point mass and ignore air resistance). They will take up as positive, and assign the zero level for the gravitational potential energy to be at the ground where the balloons will land.

Prelecture n in a Block-Spring System Terry and Jolon are enjoying their physics class, and want to learn more about work and energy. They decide to stay after class to discuss the topics and see whether they can gain a better understanding. They use this simulation to help them. The system in this simulation consists of the block and the spring. In the simulation, the friends should assume that the surface is level and frictionless. They can use the mouse to move the block and compress the spring, then let the block go to release it. They should note that the energy diagram shows the kinetic, potential, and total mechanical energies of the block-spring system. fonce elocily PotentialTetal Display in a New Window Part 1 of 12-Energy in a System During their discussion, Jolon makes several statements about energy. Which statement is correct? Energy in a system changes depending on what kind of energy is in the system. Energy in a system always switches between kinetic and potential forms." Energy in a system can be increased if work is inserted into the system from outside." Energy in a system is always constant." Submit cannot come

Explanation / Answer

During the compression work is done on the system which is stored in the spring in the form of potential energy. We can increase the potential energy by increasing the external work.
Once we compress the spring and release the block then considering block+spring as a system no external force is doing work. So the mechanical energy (kinetic energy + potential energy) remains conserved. Then after releasing the block the spring compression decreases and the decrease in potential energy of the spring changes into the kinetic energy of the block. But it do not switch again and again. After the spring has relaxed all the potential energy of the spring converts into kinetic energy of the block.

If we consider that work has done on the system then energy of the system will be constant after work done. But the energy of the system can be increased using work on the system.

So the last option should be correct.

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