Knowing the length of your stride will allow you to determine the circumference of a ride (from which the radius can then be calculated) or aid in determining the vertical height of the ride.

a) Determine the length of your stride: At normal pace, walk the length of the Bryan fourth floor hallway. Count the number of steps required to travel this distance, and then use the known distance (in meters) to determine your average distance covered per step. Show all measurements and calculations.

b) For pre-state fair practice, determine the distance from Bryan front door to the street curb at Club and 9th. Show work below, with units. Partners should compare answers. The directly measured distance will later be given.

2) VERTICAL DISTANCE: TRIANGULATION

The horizontal accelerometer contains a straw (for sighting) and a protractor (for angle measurement) that can be combined with a known horizontal distance (measured, for example, by pacing) to determine the height of tall objects. This method can be used to determine ride height at the State Fair.

Suppose that the top T of a ride is at height h above level ground and that you are at point S in the diagram shown below.

                                T

                                h
     q_f
 F                              B
 
 

S                                   q _i
                                              d
 
 
 

a) The first task is to measure the angular height, q_i, in degrees, of the top of the ride as seen from point S.

The picture below shows how an angle q can be determined by the straw-protractor combination. In

sighting some mark at an angular height q to the ground, note that the angle q is the difference between

the position of the middle BB and the q = 0° mark on the protractor.

Sight the top of the ride through the straw and have your partner read the angle of inclination (to the horizontal) of the straw; this is done by noting the angle on the protractor at which the middle BB rests. Call this angle q _i.

b) Now pace off a known distance d directly toward the object whose height is to be determined. You are now at point F. (See the diagram on the previous page.) It is important that:

(1) the ground be relatively level between S and F

and (2) the distance d be a large fraction of the total distance from the start S to the base B of the ride.

Again sight the same point on the top of the ride through the straw and have your partner read the straw’s new angle of inclination. This angle, q _f, is marked on the diagram on the previous page.

c) The height h can then be calculated from

h = observer’s height + d * sin q _i * sin q _f / sin(q_f - q _i)
 
 

d) If you can walk to the base B of the height h being measured, q _f = 90° and sin q _f = 1, and the expression

above reduces to

h = observer’s height + d * tan q _i

e) For pre-state fair practice, determine the height of the Bryan 4th floor dorm windows above the front

Bryan lawn without walking directly to the base of the dorm. Measure to the top of the windows. Make a large diagram that shows all measurements; show all calculations neatly. Label all numbers with appropriate symbols ! How many sets of measurements should you make?