Time Rates

38 - Rate of rotation of search light pointing to a ship

Problem 38
A ship, moving 8 mi/hr, sails north for 30 min, then turns east. If a searchlight at the point of departure follows the ship, how fast is the light rotating 2 hr after the start.
 

37 - A ladder sliding downward

Problem 37
A ladder 15 ft long leans against a vertical wall. If the top slides down at 2 ft/sec, how fast is the angle of elevation of the ladder decreasing, when the lower end is 12 ft from the wall?
 

37-38 How fast a ship leaving from its starting point

Problem 37
A ship sails east 20 miles and then turns N 30° W. If the ship's speed is 10 mi/hr, find how fast it will be leaving the starting point 6 hr after the start.

35-36 Time Rates: Lengthening of shadow and movement of its tip in 3D space

Problem 35
An arc light hangs at the height of 30 ft above the center of a street 60 ft wide. A man 6 ft tall walks along the sidewalk at the rate of 4 ft/sec. How fast is his shadow lengthening when he is 40 ft up the street?

33-34 Time Rates: A car traveling east and airplane traveling north

Problem 33
From a car traveling east at 40 miles per hour, an airplane traveling horizontally north at 100 miles per hour is visible 1 mile east, 2 miles south, and 2 miles up. Find when this two will be nearest together.

31-32 Train in an elevated track and car in perpendicular road

Problem 31
An elevated train on a track 30 ft above the ground crosses a street at the rate of 20 ft/sec at the instant that a car, approaching at the rate of 30 ft/sec, is 40 ft up the street. Find how fast the train and the car separating 1 second later.

30 - Two trains in perpendicular railroad tracks

Problem 30
Two railroad tracks intersect at right angles, at noon there is a train on each track approaching the crossing at 40 mi/hr, one being 100 mi, the other 200 mi distant. Find (a) when they will be nearest together, and (b) what will be their minimum distance apart.
 

28-29 Time Rates: Two cars driving on roads that intersects at 60 degree

28-figure-48.jpgProblem 28
At noon a car drives from A (Fig. 48) toward C at 60 miles per hour. Another car starting from B at the same time drives toward A at 30 miles per hour. If AB = 42 miles, find when the cars will be nearest each other.
 
 

26-27 Time Rates: Kite moving horizontally

Problem 26
A kite is 40 ft high with 50 ft cord out. If the kite moves horizontally at 5 miles per hour directly away from the boy flying it, how fast is the cord being paid out?

Pages

Subscribe to RSS - Time Rates