Answer:
The second dart leaves the gun two times as faster than the first one.
Explanation:
Assuming no energy loss during the spring-dart energy transfer, we have by the conservation of energy principle

Given an arbitrary
and its double,
, launch velocities are

Given
Three 7 ohm resistor are in series.
The battery is V=10V
To find
The equivalent resistance
Explanation
When the resistance are in series then the resistance are added to find its equivalent.
Thus the equivalent resistance is:

Conclusion
The equivalent resistance is 21 ohm
Answer:
22 degree
Explanation:
Angle of incidence, i = 30 degree
the refractive index of water with respect to air is 4/3.
As the ray of light travels from rarer medium to denser medium, that mean air to water, the refraction takes place.
According to Snell's law,
Refractive index of water with respect to air = Sin i / Sin r
Where, r be the angle of refraction
4 / 3 = Sin 30 / Sin r
0.75 = 2 Sin r
Sin r = 0.375
r = 22 degree
Thus, the angle of refraction is 22 degree.
Answer:
Distance of the point where electric filed is 2.45 N/C is 1.06 m
Explanation:
We have given charge per unit length, that is liner charge density 
Electric field E = 2.45 N/C
We have to find the distance at which electric field is 2.45 N/C
We know that electric field due to linear charge is equal to
, here
is linear charge density and r is distance of the point where we have to find the electric field
So 
r = 1.06 m
So distance of the point where electric filed is 2.45 N/C is 1.06 m