Answer:
Average speed will be 48.23 km/h
Explanation:
Let the distance up to hill is = d km
Speed when car goes to hill = 38 km/h
So time required
Speed when car return from hill = 66 km/h
So time required to return fro hill
Total time
Total distance = d+d =2d
So average speed
When boat is sunk into the liquid the net buoyancy on the boat is counterbalanced by weight of the boat
So here weight of the boat = Buoyancy force
let say boat is sunk by distance "h"
now we can say
now by above force balance equation we can write
so boat will sunk by total 5 mm distance