Answer:


Explanation:
m = Mass of each the cars = 
= Initial velocity of first car = 3.46 m/s
= Initial velocity of the other two cars = 1.4 m/s
v = Velocity of combined mass
As the momentum is conserved in the system we have

Speed of the three coupled cars after the collision is
.
As energy in the system is conserved we have

The kinetic energy lost during the collision is
.
Answer:
The frequency increases.
Explanation:
When the Musician draws the slide in the length of the horn gets shorter, which causes a decrease in the wavelength. A decrease in the wave length results in an increase in frequency.
Note:
The diameter of the horn has an effect on frequency, so a wider horn is effectively a long horn - open end correction ( distance between the the antinode and the open end of a pipe).
Frequency also depends on how hard the musician blows the trombone. The musician can change the frequency with the lip pressure being applied.
Answer:
His average speed is 980 units
Answer:
the electric field strength of this charge is two times the strength of the other charge
Explanation:
Using the relationship between electric field and the charge, which is inversely proportionality. Let the the magnitude of the first charge be Q and the respective electric field be E. It implies that;
E1/E2 = Q2/Q1
E2 = E1 x Q1/Q2
= E x Q/ (Q/2)
= 2E
A closed system is a system that is completely isolated from its environment. The physical universe, as we currently understand it, appears to be a closed system. An open system is a system that has flows of information, energy, and/or matter between the system and its environment, and which adapts to the exchange.
D makes the most sense, but you just have to put two and two together and go with your gut feeling, first cross out the answers that don't make sense (A didnt make sense) and go from there! I hope the little bit above me helped you answer or decide :) Good luck!