Why is it possible to do the following party tricks without cheating? A. Stand with back and heels touching a wall and bend forward from the hips to touch the floor. Return to the upright position without flling or moving the root.
B. Stand facing the edge of an open door with nose and abdomen touching the edge, the feetstraddling the door, and the hands to the sides. Attempt to rise up on the toes. Observe what body motions occur to keep the center of gravity within the base of support whenthese activities are performed without the impediments.

When the body is supported by a wall then it can move in a position counter gravity. The gravity tries to pull the body down and the body responds to it with a slight delay because of wall support.

Explanation:

The body is lifted in upright position with the help of feet. The body rises but after few minutes the gravitational force creates pressure on the body and the body comes down to a natural state. Similarly if the open door is used to perform counter gravity activities then the body will stay for a lesser period in a state because of opened door instead of firm wall support.

measuring light intensity

light meters can be used to measure light intensity. the meter is held at the soil surface and pointed in the direction of the maximum light intensity, and then the meter is read.

errors can be made when measuring light intensity by accidentally shading the light meter. the reliability of the results can be checked by taking many samples.