Answer:
velocity at the top: 0 m/s
acceleration at the top: -9.8 m/s²
Explanation:
Assuming up is positive and down is negative;
The velocity of the ball at the top of its path will be 0 m/s and the acceleration will be negative.
The velocity is 0 m/s because the ball does not move at the top of its path, and it switches from a positive velocity to a negative velocity. It must go through 0 in order to go from positive to negative.
The acceleration, however, is always negative no matter where the ball is in its motion. This negative acceleration causes the ball to slow down as it reaches the top, and speed up as it reaches the bottom.
<u>Think about it:</u> If there wasn't a negative acceleration, and it was instead 0, the ball would never come back down and instead keep going in a straight line.
The average speed of the car for the entire trip can be calculate by using:
where S is the total distance covered by the car, and t is the total time taken.
The total distance travelled by the car is:
while the total time taken is:
so, the average speed of the car is:
so, the correct answer is (3) 85 km/h.
Wavelength = speed / frequency
(345 m/s) / (20,000 Hz) = 0.017 m
ANSWER
EXPLANATION
Parameters given:
Initial velocity, u = 26.2 m/s
When the vase reaches its maximum height, its velocity becomes 0 m/s. That is the final velocity.
We can now apply one of Newton's equations of motion to find the height:
where a = g = acceleration due to gravity = 9.8 m/s²
Therefore, we have that:
That is the height that the vase will reach.
Light that enters the new medium <em>perpendicular to the surface</em> keeps sailing straight through the new medium unrefracted (in the same direction).
Perpendicular to the surface is the "normal" to the surface. So the angle of incidence (angle between the laser and the normal) is zero, and the law of refraction (just like the law of reflection) predicts an angle of zero between the normal and the refracted (or the reflected) beam.
Moral of the story: If you want your laser to keep going in the same direction after it enters the water, or to bounce back in the same direction it came from when it hits the mirror, then shoot it <em>straight on</em> to the surface, perpendicular to it.
