Featured in PASCO’s Advanced Physics Teacher Guide

Advanced Physics Teacher Guide

(PS-2879C)

This manual features over 30 College Board curriculum and AP Physics exam inspired lab activities.

Work and Power

Lab Summary

Use a force sensor, a photogate, and a meter stick to determine the amount of work done by a high-friction surface to stop a runaway cart. Calculate the power dissipated by friction in each trial.

Theory

A cart with mass m speeds down an inclined track into a flat section with constant velocity v0, then leaves the track and continues onto a high friction surface designed to stop the cart after a distance d.

  • Measure the stopping distance d of the cart as a result of different v0 values, then use your data to determine the mathematical relationship between d and v0.
  • Determine the amount of power dissipated in stopping the cart for each trial.
  • Predict the distance d needed to stop a runaway cart with mass m and velocity v0, considering that the only force doing work to stop the cart is the frictional force from a runaway cart pad.

 

Method

  • Students gain experience conducting the following procedures:
  • Using the work-kinetic energy theorem to determine that the kinetic energy at the bottom of the track is equal to the work necessary to stop the cart: ΣW = Kf − Ki where
    Ki = 1/2 mv2 ;
    Kf = 0
    ; and ΣW = μkmgd ; or d = v2/2μkg
  • Holding the cart at a given distance up on the inclined track to produce a constant (reproducible) velocity as the cart passes onto the friction pad.
  • Measuring the velocity of the cart at the bottom of the track just before it travels onto the friction pad, and the stopping distance d.
  • Plotting a linear relationship between d and v to determine that d is proportional to v2.

Sensors / Equipment Used:

PASPORT High Resolution Force Sensor

(PS-2189)

Designed to measure both pulling and pushing forces. Provides a very high resolution of data collection.

PASPORT Digital Adapter

(PS-2159)

The Digital Adapter allows ScienceWorkshop analog sensors to be connected and used with PASPORT interfaces.

Basic PAStrack Dynamics System

(ME-6962)

Two half-meter tracks designed to accept carts from the Dynamics Systems to study various motion related experiments.

Photogate Head

(ME-9498A)

Monitors the motion of objects passing through its gate, counting events as the object breaks the infrared beam. For use with PASPORT and ScienceWorkshop Interfaces.

Cart Picket Fences (2 Pack) -- IDS

(ME-9804)

Replacement photogate fences that mount on Dynamics Carts.

Photogate Brackets (2 Pack) -- IDS

(ME-9806)

The Photogate Bracket is designed to attach Photogate Head to PAStrack and Curved PAStrack.

Track Rod Clamp

(ME-9836)

Fastens to the T-Slot of a Dynamics track and accepts a 1/2 inch rod.

Base and Support Rod

(ME-9355)

The Large Base and Support Rod includes built-in leveling screws and an aluminum rod that is 12.7 mm (1/2 in.) in diameter and 45 cm long.

Materials Used:

Meter stick
Stop watch
String
Balance, 1200-g capacity 
Carpet strip or other high-friction surface

The Associated Bundle:

Advanced Physics Standard Sensor Bundle

(PS-2932B)

This bundle contains the probeware needed to perform all 37 lab activities in the Advanced Physics lab manual.

Interface Required

This experiment may require software and an interface for data collection.