A disc of radius R=20cm is rotating about its axis with an angular velocity ω=20rads-1 on a horizontal smooth surface. The linear speed of point C on the disc is
Correct answer: D. 4ms-1
- A. 1ms-1
- B. 3ms-1
- C. 2ms-1
- D. 4ms-1
Explanation
The linear speed v of a point on a rotating disc is calculated using the formula v = r * ω, where r is the radius in meters and ω is the angular velocity in radians per second. Given the radius r = 20cm = 0.2m and angular velocity ω = 20rads-1, we calculate v = 0.2m * 20rads-1 = 4m/s. This makes Option D correct. Options A, B, and C result from incorrect calculations or a misunderstanding of unit conversions.
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About Angular and Linear Quantities
Rotational motion relates angular displacement, angular velocity and angular acceleration to linear displacement, tangential velocity and tangential acceleration through the radius. Questions use radians, v equals r omega and tangential acceleration, while distinguishing tangential velocity from centripetal acceleration and angular quantities from their linear counterparts.
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