My PBL Project

Introduction:

Why does the temperature of a small steel plate increase when it is hit repeatedly with small steel balls?

Finding the mechanical equivalent of heat through rotating a plastic tube filled a small amount of metal balls, calculating the temperature change in the metal balls when hitting the temperature sensors at the bottoms of the tube.

Materials:

♦ PASCO Mechanical Equivalent of Heat Tube

♦ PASCO Data collection system

♦ PASCO Temperature sensor

♦ Laptop with PASCO software

Procedure:

PART 1: Assemble the Mechanical Equivalent of Heat Tube and place the small steel balls into it. Connect the built-in temperature sensor to the data collection system and begin recording data at a high sample rate. Invert the tube several times, allowing the steel balls to strike the metal plate inside the tube.

PART 2: Assemble the Thermal Hammer and place the small steel balls into it. Connect the built-in temperature sensor to the data collection system and begin recording data at a high sample rate. Strike the Thermal Hammer several times onto the foam pad.

PART 3: After recording the data check the program and review it after performing trial runs with multiple metal balls; the amount varying with each trial.

Scientific Principle:

WORK

Work results when a force acts upon an object to cause a displacement (or a motion) or, in some instances, to hinder a motion. Three variables are of importance in this definition - force, displacement, and the extent to which the force causes or hinders the displacement. Each of these three variables find their way into the equation for work. That equation is:

Work = Force • Displacement • Cosine(theta)

W = F • d • cos(theta)

Since the standard metric unit of force is the Newton and the standard meteric unit of displacement is the meter, then the standard metric unit of work is a Newton•meter, defined as a Joule and abbreviated with a J.

HEAT

Specific heat capacities provide a means of mathematically relating the amount of thermal energy gained (or lost) by a sample of any substance to the sample's mass and its resulting temperature change. The relationship between these four quantities is often expressed by the following equation.

Q = m•C•ΔT

Where Q is the quantity of heat transferred to or from the object,m is the mass of the object, C is the specific heat capacity of the material the object is composed of, and ΔT is the resulting temperature change of the object. As in all situations in science, adelta (?) value for any quantity is calculated by subtracting the initial value of the quantity from the final value of the quantity. In this case, ΔT is equal to Tfinal - Tinitial. When using the above equation, the Q value can turn out to be either positive or negative. As always, a positive and a negative result from a calculation has physical significance. A positive Q value indicates that the object gained thermal energy from its surroundings; this would correspond to an increase in temperature and a positive ΔT value. A negative Q value indicates that the object released thermal energy to its surroundings; this would correspond to a decrease in temperature and a negative ΔT value.

Knowing any three of these four quantities allows an individual to calculate the fourth quantity. A common task in many physics classes involves solving problems associated with the relationships between these four quantities.

Safety Measures:

Pay attention to the following maintenance recommendations, and add these important safety precautions to your normal laboratory procedures:

♦ Be certain that the end caps and steel plate are secure before using the Mechanical Equivalent of Heat Tube.

♦ Do not hit the Thermal Hammer on anything but the included foam pad.

♦ Do not hit the Thermal Hammer excessively hard on the foam pad as this may damage it.