Answer
The answer to this question is 
Explanation
As we know that accelartion is the rate of change of velocity. So, it can be write as

where
is the final velocity
is the initial velocity
t is the time
a is the accelartion
as we konw

t = 10 s
From rest So,
= 0
= ?
Putting values




So, the right answe is 
70x3=210 mph... its that easy
Explanation:
The nearest star to the Earth is the red dwarf star Proxima Centauri, at a distance of 4.218 light-years.
Light year is the unit of distance covered by the heavenly bodies. 1 light year is equal to :
So,
We need to convert 4.218 light-years barley corns.
Since, 1 barleycorn = 1/3 inch


So, the nearest star to the Earth is at a distance of
. Hence, this is the required solution.
The text does not specify whether the resistance R of the wire must be kept the same or not: here I assume R must be kept the same.
The relationship between the resistance and the resistivity of a wire is

where

is the resistivity
A is the cross-sectional area
R is the resistance
L is the wire length
the cross-sectional area is given by

where r is the radius of the wire. Substituting in the previous equation ,we find

For the new wire, the length L is kept the same (L'=L) while the radius is doubled (r'=2r), so the new resistivity is

Therefore, the new resistivity must be 4 times the original one.