A grinding wheel is spinning at a rate of 20.0 revolutions per second. When the power to the grinder is turned off, the grinding wheel slows with constant angular acceleration and takes 80.0 s to come to a rest

(a) What was the angular acceleration of the grinding wheel as it came to rest? (b) How many rotations did the wheel make during the time it was coming to rest?


(a) 1.57 rad/s2
(b) 800 revolutions

Physics & Space Science

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Thermal Expansion: A brass rod is 69.5 cm long and an aluminum rod is 49.3 cm long when both rods are at an initial temperature of 0° C. The rods are placed in line with a gap of 1.2 cm between them, as shown in the figure. The distance between the far ends of the rods is maintained at 120.0 cm throughout. The temperature of both rods is raised equally until they are barely in contact. At what temperature does contact occur? The coefficients of linear expansion of brass and aluminum are 2.0 × 10-5 K-1 (brass) and 2.4 × 10-5 K-1 (aluminum). 

A. 470°C B. 440°C C. 420°C D. 490°C E. 510°C

Physics & Space Science

What would happen if a small piece (say the size of a paper clip) of neutron star material suddenly appeared on Earth?

What will be an ideal response?

Physics & Space Science

Although it is difficult to tell from our vantage point inside the galaxy, astronomers suspect that the Milky Way is a barred spiral

Indicate whether the statement is true or false

Physics & Space Science

The colonization of land by plants appears to have begun about

A) 542 million years ago B) 360 million years ago C) 65 million years ago D) 475 million years ago

Physics & Space Science