Answer:
The new speed is 56.25 miles/hour.
Explanation:
Since speed = distance/time;
time = distance/speed.
While driving at 50 miles/hour, time taken for one to complete 1 mile is (1/50) hour
(1/50) hour = (1/50) × 3600s = 72 seconds.
So, if this time to complete 1 mile (72 seconds) is reduced by 8 seconds,
New time to complete 1 mile will be = 72 - 8 = 64 seconds = (64/3600) hour = 0.0178 hour
New speed would be = (1 mile/64 seconds) = (1 mile/0.0178 hour) = 56.25 miles/hour.
Hope this Helps!!!
Answer:
Second Trial satisfy principle of conservation of momentum
Explanation:
Given mass of ball A and ball B 
Let mass of ball
and
Final velocity of ball 
Final velocity of ball 
initial velocity of ball 
Initial velocity of ball 
Momentum after collision 
Momentum before collision 
Conservation of momentum in a closed system states that, moment before collision should be equal to moment after collision.
Now, 
Plugging each trial in this equation we get,
First Trial

momentum before collision
moment after collision
Second Trial

moment before collision
moment after collision
Third Trial

momentum before collision
moment after collision
Fourth Trial

momentum before collision
moment after collision
We can see only Trial- 2 shows the conservation of momentum in a closed system.
When a crest-trough meet the interference produced will be destructive in nature hence they both will cancel out and the amplitude produced will be equal to zero hence the loudness will reduce to zero.