BHS > Staff > Mr. Stanbrough >IP HowTo Notes > this page
A ball is kicked with an initial speed of 24.0 m/s at an angle of 38.0^{o} from the horizontal...
but Interactive Physics^{TM} does not seem to have a convenient, straightforward way to give an object a particular starting speed in a particular direction. Fear not!
This object will have a starting velocity of 24.0 m/s at an angle of 38^{o} from the horizontal. 

and then enter the results in the v_{x} and v_{y} fields of the object's Properties Window. In the example above, for instance:
v_{x} = (24.0 m/s) cos (38.0^{o}) = 18.912 m/sv_{y} = (24.0 m/s) sin (38.0^{o}) = 14.776 m/s
In order to change the starting speed or angle, you will need to
recalculate the velocity component's values and reenter them in the
Properties Window.
This object also has a a starting velocity of 24.0 m/s at an angle of 38^{o} from the horizontal. 

You need to be aware, however, that Interactive Physics^{TM} deals only with angles in radians, so a simple degreestoradians conversion has to be done many cases. (That is what the "pi/180" in the example at right does.)
To change the speed and/or angle values, you can edit the
v_{x} and v_{y} fields in the object's Properties
Window.
Selecting "Speed and Direction" from the "New Controls" submenu of the Define Menu adds these two controls to the simulation. 

Here is the Properties Window. 

At right is a screen shot of the simulation, ready to start. The speed of the ball will be 24.0 m/s at an angle of 38^{o}. 

The Properties Window for the projectile. The formulae for the velocity components have been modified to convert the input to degrees. 

The Properties Window for the Speed control. Speeds can be from 0 to 30 m/s, in increments of 1 m/s. Of course, any value in the allowable range can be typed into the text box. 

The Properties Window for the Direction control. Directions between 0 and 90^{o} in increments of 1^{o} can be selected on the slider. 

Remember that Interactive Physics^{TM} works in
radian mode. If you want to specify direction in degrees, the example
Properties Window at right shows how to do it.