Hi there! i have this question about turning forces and i'm a bit confused with the centre of mass and pivot question.

jic the pic cant be seen:
a uniform metre ruler pq is in equilibrium.
the distance pq is 100cm
the mass of the metre ruler is 0.12kg and its weight is w.
point p is 10cm from the pivot and has a weight of 0.5n hanging from it. point q has a force going upwards on it.

question: on the fig. draw
1. an arrow to shoe force w acting in pq at the centre of mass
2. an arrow to show the force r acting at the pivot.

An object is dropped from a tower, 400 ft above the ground. the object's height above ground t seconds after the fall is s(t)equals400 minus 16 t squared. determine the velocity and acceleration of the object the moment it reaches the ground. the velocity of the object the moment it reaches the ground is nothing ft/s.

The key to stability is feedback between the reservoir and the fluxes into and/or out of the reservoir. assume that the rate of outflow from a reservoir depends on the size of the reservoir according to the following relationship: outflow rate= k x (size of reservoir), where k is a constant. a reservoir of water has a volume of 5000 liters, and the rate of outflow at steady state is 25 liters per minute. what is k? (give both the numerical value and its units.) what is the residence time? what is the relationship between k and the residence time?

The plum pudding model of the atom state that ?