Final answer:
A good-quality measuring tape off by 0.50 cm over 20 m has a 0.0025% percent uncertainty. Expansion gaps for steel rails account for thermal expansion due to temperature changes.
Step-by-step explanation:
The correct answer is option percent uncertainty of a measuring device. For example, a good-quality measuring tape that can be off by 0.50 cm over a distance of 20 m has a percent uncertainty calculated by dividing the error by the total distance and then multiplying by 100 to get the percentage.
The correct formula for this calculation is (0.50 cm / 20,000 cm) × 100%, which results in a percent uncertainty of 0.0025%.
To address questions related to track widths and expansion gaps for steel railroad rails, one must understand the concept of thermal expansion. Steel rails expand when heated, and the appropriate gap must be left to accommodate this expansion.
The expansion gap would be determined by the coefficient of thermal expansion for steel and the original length of the rails, in addition to the maximum temperature change they are expected to experience.
The correct answer is option (c). In this question, the student is asking about the maximum difference (%) between the track widths when the temperature of the steel railroad rails reaches a maximum temperature 35.0°C greater than when they were laid, given their original length of 10.0 m.
To calculate the maximum difference (%) between the track widths, we need to consider the thermal expansion of the steel rails. The expansion of a material due to temperature change is given by the equation: ΔL = αL0ΔT, where ΔL is the change in length, α is the coefficient of linear expansion, L0 is the original length, and ΔT is the change in temperature.
By substituting the values into the equation, we can calculate the change in length, and consequently, the maximum difference (%) between the track widths. The coefficient of linear expansion for steel is approximately 12 x 10^-6 1/°C. Using this information, we can find the maximum difference (%) between the track widths.