Answer: New speed of car is 30.0 mph
Explanation:
Since speed is equal to the distance traveled divided by time taken ,i.e.,
Speed , [tex]Speed (V)=\frac{Distance (D)}{Time(T)}[/tex]
Case 1
[tex]V_1=15 mph , Distance = D_1,time=T_1[/tex]
=>[tex]15 mph =\frac{D_1}{T_1}[/tex]
Case 2
[tex]V_2=? mph, D_2=D_1 , T_2=\frac{T_1}{2}[/tex][tex]=0.5T_1[/tex]
=>[tex]V_2=\frac{D_2}{T_2}=\frac{D_1}{.5T_1}=2V_1[/tex]
=>[tex]V_2=2V_1=2\times 15 mph=30mph[/tex]
Thus new speed of car is 30.0 mph