A radar receiver indicates that a pulse return as an echo in 20 μs after it was sent. The reflecting object would be 3000 m away .
Phenomenon of hearing back our own sound is called an echo. It is due to successive reflection of sound waves from the surfaces or obstacles of large size. To hear an echo, there must be a time gap of 0.1 second in original sound and the reflected sound.
Given
time = 20 μs = 20 *
s
let distance to the reflecting surface be = x
total distance travelled by pulse will be = 2x
speed = 3.0 ×
m/s
distance = speed * time
2x = 3.0 ×
* 20 *
x = 3000 m
The reflecting object would be 3000 m away
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Position 1 I believe because that is when the potential energy is released on the downfall
Friction , as the angle gets huger and higher , this is less and less normal force into the inclined plane .
Answer:
The correct answer is option a.
Explanation:
Conservation of momentum :

Where :
= masses of object collided
= initial velocity before collision
= final velocity after collision
We have :
Two equal-mass carts roll towards each other.

Initial velocity of 
Initial velocity of
(opposite direction)
Final velocity of
(same direction )
Final velocity of
(same direction)


v = 0.5 m/s
rg135
The speed of the carts after their collision is 0.5 m/s.