C. Negative force. The dog isn't going to learn that way.
we know that
Power efficiency is defined as the ratio of the output power divided by the input power:
so
in this problem
Substitute in the formula above
%
therefore
the answer is
the efficient is 
%
Light is a very complex phenomenon, but in many situations its behavior can be understood with a simple model based on rays and wave fronts. A ray is a thin beam of light that travels in a straight line. A wave front is the line (not necessarily straight) or surface connecting all the light that left a source at the same time. For a source like the Sun, rays radiate out in all directions; the wave fronts are spheres centered on the Sun. If the source is a long way away, the wave fronts can be treated as parallel lines.
Rays and wave fronts can generally be used to represent light when the light is interacting with objects that are much larger than the wavelength of light, which is about 500 nm. In particular, we'll use rays and wave fronts to analyze how light interacts with mirrors and lenses.
A! The bright light will have taller more spread out waves while the dimmer light will have smaller closer together waves. Hope this helps!
Answer:
2.1 s
Explanation:
The motion of the ball is a projectile motion. We know that the horizontal range of the ball is
And that the initial speed of the ball is
at an angle of
So, the horizontal speed of the ball (which is constant during the entire motion) is
And since the horizontal range is 50 m, the time taken for the ball to cover this distance was
which is the time the ball spent in air.
