The scientific unit for speed is kilometers per hour, hope this helps
The time (t) it will take for the train to reach to Grenoble is the quotient when the distance (d) is divided by the speed (s). That is,
t = d / s
Substituting the known values,
t = 480 km / 180 km/h
t = 2.667 h
Thus, it will take approximately 2.7 h to reach Grenoble. The answer is letter D.
Explanation :
When a person is sliding with constant velocity, the forces that are acting on him are :
(1) Weight, W = mg where g is acceleration due to gravity.
(2) Friction forces acting opposite to the direction of motion.
(3) Normal force.
The forces acting on the person is balanced because the person is sliding with constant velocity.
From figure it is clear that, friction force is balanced by
and normal is balanced by
.