Answer: TWO.
At least two groups: treatment group and control group.
The treatment group is that is exposed to the different levels of the independent variable ( a medication for example), while the control group is not treated, so the researchers can compare the effect of the medication.
The independent variable would be the variable in the research that is being manipulated by the researcher. In this case, it would be amount of food as it is what is being manipulated and changed in the research design. The dependent variable would be the variable that is being studied so, for this case, it would be the weight gain of the mice. The constants are the factors that might affect the dependent variable but is held constant or the same by the researcher throughout the experiment. These are the size of cage, amount of water, amount of sunlight, temperature and the exercise wheel.
Answer:
b) velocity.
c) velocity, m/s²
d)change in velocity, change in direction, change in both velocity and direction.
e) increasing or decreasing
The mass of ore required is
21 700 t.
r = 750 cm
V =

=

= 1.767 × 10⁹ cm³
The density of lead is 11.34 g/cm³.
So mass of lead sphere = 1.767 × 10⁹ cm³ ×

= 2.004 ×10¹⁰ g
2.004 ×10¹⁰ g ×

= 2.004 × 10⁷ kg
2.004 × 10⁷ kg ×

= 2.004 × 10⁴ t
92.5% efficiency means 92.5 t Pb per 100 t of ore.
Mass of ore = 2.004 × 10⁴ t Pb ×

= 2.17 × 10⁴ t ore = 21 700 t ore