1
Q
the plank is uniform
A
Assuming the plank is uniform means the weight of the plank acts at its centre of mass: i.e. halfway along the plank.
2
Q
the plank is a rod
A
Assuming the plank is a rod means its width can be ignored.
3
Q
the man is a particle
A
Assuming the man is a particle means all his weight acts at the point at which he stands.
4
Q
state assumption you have made in your calculations and comment on the validity of each assumption
A
that the ball behaves as a particle
that acceleration due to gravity remains constant over the distance fallen
