"Reflection" is the change direction of waves when blocked by obstacle
When smoke particles pass between the source of radiation and the detector the drop in radiation will be sufficient to tigger the alarm. <span />
Answer:
, downward
Explanation:
There is only one force acting on the ball during its motion: the force of gravity, which is given by

where
m is the mass of the ball
is the acceleration of gravity (downward)
According to Newton's second law,

where F is the net force on the object and a is its acceleration. Rearranging for a,

As we said, the only force acting on the ball is gravity, so F = mg and the acceleration of the ball is:

Therefore, the ball has a constant acceleration of
downward for the entire motion.
The answer is B
As seen on the graph, the bus maintains a 9m/s speed for a majority of the trip to school.