Passage V

A block is placed on an inclined plane, as shown in Figure 1.

The angle of inclination is increased. The angle at which static friction is overcome and the block starts to slide is αc, the critical angle for sliding. The amount of static friction to be overcome depends on µ, the coefficient of static friction.

Table 1 gives αc and µ for a steel block sliding on various uncoated surfaces at 20°C. Tables 2 and 3 give αc and µ for the steel block sliding on a steel surface coated with various oils at 20°C and 100°C, respectively.

25. Based on the data in Tables 2 and 3, which of the following bar graphs best represents µ for light machine oil and thick gear oil at 20° and 100°C ?

Answer and Explanation

Your Answer is

Correct Answer is B

Explanation

Look at table first, at 20 degrees, μ=0.16 of light machine oil, and μ=0.13 of thick gear oil;

Look at table 3 again, at 100 degrees, μ=0.19 of light machine oil , μ=0.15 of thick gear oil. For the two oils, the general trend is that the higher the temperature, the larger the μ, so the option B is in line with this general trend