How to Make an Energy Bar Chart 1

How to Make an Energy Bar Chart 1. Determine what is in the system

2. Choose a height for each bar. Draw a bar for each kind of energy in the system. • there is no kinetic and elastic potential energy in the initial state • there is no gravitational and elastic potential energy in the final state • there is no work done by external forces • the sum of the heights on the right (5 units) equals the sum of the heights on the left (5 units)

3. If energy leaves or enters the system, make a bar for work done by the system (example: heat lost because of friction)

Or work done on the system (skier’s poles moving a skier faster)

Stephen is pulling David up at a constant speed on a frictionless water slide. Construct a statement involving energy and work that best describes Which of the following statements the situation. best describes the situation? System 40 o Earth 1 The energy in the system changes. This change is equal to the force that Stephen exerts on David multiplied by the distance David moves. 2 The energy in the system changes. This change is equal to the force that Stephen exerts on David multiplied by the distance David moves multiplied by the cos 40 o. 3 David is moving at a constant speed, thus the net force exerted on David is zero. Zero net force means zero work. Thus, the energy of the system does not change.

situationisisdescribedwithaabar barchart. and Construct AAsituation in words. a verbal description matches this bar chart. Which verbalthat description this bar chart? Kinitial + Ug initial + Us initial + W = Kfinal + Ug final + Us final +DEint 1 An object fell off a cliff and energy in the system was transferred from gravitational potential energy to kinetic energy. 2 A spring on a table shot an object. You measured the kinetic energy of the object when it landed at the same elevation. 3 A spring shot an object vertically from a height above the ground. You then measure the kinetic energy at ground level just before the ball hits the ground.

AA situation is is represented pictorially below. Construct Which bara bar chart best matches the picture. chart bestthat matches the picture? system y t, y = h ti, yi = 0 v = constant Earth Ko + 1 2 3 Ugo W K + Ug + Us

Tim is carrying a basket of laundry to be washed. This motion is represented by a free body diagram and a motion diagram. y = constant x Earth Which verbal description best that Construct a verbal description matches the diagrams? (The earth best matches the diagrams. and basket are the system) earth and basket are the system) 1 Since the basket is moving, work is done on the basket and that is all we are able to tell. 2 Tim does work, but the systems energy does not change. 3 The velocity is constant, the height is constant and Tim is doing work. The internal energy of the system must be increasing. 4 No work is being done on the system which implies the system’s energy does not change.

Alan is on a frictionless kiddie coaster. Which energy bar chart Construct an energy bar best matches chart that bestthis matches situation as the car this situation as the car goes to to the bottom? goes 1 2 Ki + Ugi W = Kf + Ugf h>hf >0 vf >0 3 hi=h vi=0 Ki + Ugi W = Kf + Ugf

the same coaster was If. If the not frictionless, which not bar chart would construct a bar chart describe that process? would describe that process. 1 2 Ki + Ugi W = Kf + Ugf + DE 3 h>hf >0 vf >0 hi=h vi=0 Ki + Ugi W = Kf + Ugf

A roller coaster car’s trip is described by the energy bar chart shown below. Ki + Ugi W = Kf + Ugf Initial Which final point in the Construct a picture below matches showing the final and the bar chart? initial points below that matches the bar chart. 1 Final 3 Final y 0 2 Final 5 Final 4 Final

The energy bar chart below represents a car’s motion. Ki + Ugi W = Kf + DE Which motion diagram matches Construct a motion diagram thatthis matches this situation? situation. 1 3 2 4

A car is moving horizontally as described by the motion diagram below. Which energy bar chart matches this? Construct an energy barbest chart that best Ki + Uthe = Kf + Umotion 2 Kdiagram. gi W gf 1 i + Ugi W = Kf + Ugf matches above 3 Ki + Ugi W = Kf + Ugf 4 Ki + Ugi W = Kf + Ugf

Tim is moving a basket of laundry and his hands exert a force on the basket equal in magnitude to the force of the Earth on the basket. Which energy bar chart(s) could match this situation? Construct an energy bar chart that could match this (The earth and basket are the system) situation. (The earth and basket are the system) 1 3 5 Ki + Ugi W = Kf + Ugf 3&4 2 4 6 Ki + Ugi W = Kf + Ugf 2, 3 & 4