Not so fast.
I think you're using 'accelerating' to mean 'speeding up', but you really need
to be more careful with it. "Acceleration" means ANY change in speed OR
direction.
If an object's speed to the left is decreasing, or its speed to the right is
increasing, then the net force on the object must be directed towards
the right.
If an object is moving with constant speed in a circular path, then it's
constantly accelerating, because its direction is constantly changing.
The force on it is always directed towards the center of the circle, so
there's one point on the path where the force is directed straight to the right.
Given:
v(final velocity)= 7.5 m/s
t(time taken to pedal along)=4.5 s
Displacement (s)=19 m
Now we know that
s=ut+1/2(at^2)
Where s is the displacement measured in m
u is the initial velocity measured in m/sec
a is the acceleration measured in m/s^2.
t is the time taken to cover this distance.
Substituting the given values in the above formula we get
19= 4.5u+1/2(a x 4.5 x 4.5)
20.25 a + 9 u = 38
Now we also know that
v= u + at
Substituting the given values in the above formula we get
7.5= u + 4.5a
Solving for u and a from the above equations we get
u = 0.944m/s
a= 1.45 m/s^2
Thus the initial velocity is 0.944 m/s
Light can reflect from mirrors because mirrors are a prism.