A particle is acted simultaneously by mutually perpendicular simple harmonic motion x=acosωt and y = asinωt. The trajectory of motion of the particle will be:

1. an ellipse

2. a parabola

3. a circle

4. a straight line

(3) Hint: The equation of motion gives the type of motion.
Step 1: Find an equation between x and y.
Given,                  x= a cos ωt                           ...(i)
                           y= asinωt                             ...(ii)
Squaring and adding Eqs. (i) and (ii):
                        x2+y2=a2 (cos2ωt+sin2ωt)=a2
x2+y2=a2                                              [cos2ωt+sin2ωt=1]
Step 2: Find the type of motion.
This is the equation of a circle.
Clearly, the locus is a circle of constant radius a.