A lighthouse on an island is 3 km away from the nearest point p on a prefectly straight beacch.The light is revolving four times per minute.How fast is the beam of light moving along the beach when it is passing a point 1 km from p?
2006-11-26 11:00:28 · 2 answers · asked by milad m 1 in Science & Mathematics ➔ Mathematics
That point is 4km away from the lighthouse. The circumference of this circle is 16pi km. It covers 16pi km 4 times in a minute, so it covers 64pi km every minute. So the speed at that point is 64pi km/m, or about 201km/m.
2006-11-26 11:04:42 · answer #1 · answered by Texas Cowgirl 3 · 0⤊ 0⤋
Hi. The radius would be 2 kilometers (3 to p and 1 back from p) or 4 kilometers (3 to p and 1 more from p). Not enough to decide so solve for both. Pi* 2r equals circumference. Multiply by 4 (4 RPM).
2006-11-26 19:07:11 · answer #2 · answered by Cirric 7 · 0⤊ 0⤋