To determine the man's speed relative to the ground, we need to consider the velocity addition principle.
The man's velocity relative to the ground will be the vector sum of his velocity relative to the train and the train's velocity relative to the ground.
The man's velocity relative to the train is given as 5 km/h in the forward direction.
The train's velocity relative to the ground is given as 70 km/h in the forward direction.
To add these velocities, we can convert them to the same units (e.g., km/h) and add them algebraically:
Man's velocity relative to the ground = Man's velocity relative to the train + Train's velocity relative to the ground
= 5 km/h + 70 km/h
= 75 km/h
Therefore, the man's speed relative to the ground is 75 km/h.