They have different mass numbers, because they have different numbers of neutrons, and neutrons have a mass of 1, meaning changing the number of them will result in a change in the mass of the element
Gravity is pulling the skydiver down therefore gravitational force
Experimental investigations<span> involve a process in which a "fair test" is designed and variables are actively manipulated, controlled, and measured in an effort to gather evidence to support or refute a </span>causal relationship<span>. Experimental investigations have a control group which does not receive any treatment. A classic example is "What is the effect of light color on plant growth?" In this experiment, the variable color of light is changed by the student. The student may compare red light to green light to natural light.
hope i helped ^_^</span>
Explanation:
The first involves keeping the surface of the concrete moist by the use ponding, spraying/sprinkling, damp sand or damp hessian.
The second prevents the loss of moisture from the concrete by covering it with polythene sheeting or leaving the formwork in place.
The third involves the use of spray or roller applied curing compounds.
Vinegar
Sugar water
Soda pop in a sealed bottle