# Work and energy

Work and Energy. General Information. Purpose. To collect and use experimental data for accelerating carts to build graphical and mathematical models for the

system. These models represent the relationships between kinetic energy and independent variables.

Equipment Available

Computer, dynamics track, dynamics track feet, electronic or triple-beam balance, extra masses for cart, mass

hanger, pulley, scissors, slotted masses, smart cart with hook, string

Description of System

A cart is accelerated as it moves along a track by a force applied to it via a rope attached to a hanging mass.

The kinetic energy of the cart, the energy associated with its motion, will be the dependent variable of interest.

Kinetic energy, K, is calculated by

K =

1

2mv2

(1.1)

where m is the mass of the cart and v is the speed of the cart.

Observe the instructor’s demonstrations of the cart’s motion and consider the following questions.

• What factors might have an impact on the motion of the cart?

• Which factors are not quantifiable or over which you have little or no control?

• Of the factors you consider, which directly relate to each other? Can you identify independent and dependent

variables?

• Predict how changes in the force applied to the cart will affect the kinetic energy of the cart. Also predict

how the kinetic energy of the cart depends on the distance the cart has moved. State not only what you

think each relationship is, but also why you think so. The relationships should be written as a proportionality

(for example, the relationship between the circumference c and diameter d of a circle is c ∝ d). Sketch your

prediction of the graphs of kinetic energy vs. force and kinetic energy vs. displacement for the cart. You

should show the shape you expect the graphs to be as well as whether the y-intercepts should be positive,

negative, or zero, but you do not need to show the scale of the graphs.

Reading

The textbook for the course defines energy as “a scalar quantity associated with the state or condition of one or

more objects”. Energy can take many forms, including light, heat, and motion of matter. Energy associated with

the motion of objects is called kinetic energy. In this experiment, you are tasked with determining what factors

impact the kinetic energy of a cart on a track.