The first pesticides relied on natural chemicals, such as those taken from chrysanthemum flowers is true
Answer:
A skater moving downhill at increasing speed
Explanation:
- A push or pul on object called force .It is of two types.
- Balanced force
- Unbalanced force
Explanation:
Formula to calculate work done by motor is as follows.
Work done by motor = 
where, g = gravitational constant = 10 
Therefore, work done by motor is as follows.
Work done by motor = 
= 100.0 J
Now, heat lost by water will be calculated as follows.
q = 
= 
= 10.0 J
Hence, heat gained by motor = heat lost by water
As, heat gained by motor = 10.0 J
So, change in energy = heat gained - work done
Therefore, change in energy will be calculated as follows.
Change in energy = heat gained - work done
= (10.0 J) - (100.0 J)
= -90.0 J
Thus, we can conclude that change in the energy of the battery contents is -90.0 J.
Complete Question:
To aid in the prevention of tooth decay, it is recommended that drinking water contain 0.800 ppm fluoride. How many grams of F− must be added to a cylindrical water reservoir having a diameter of 2.02 × 102 m and a depth of 87.32 m?
Answer:
2.23x10⁶ g
Explanation:
The concentration of the fluoride (F⁻) must be 0.800 ppm, which is 0.800 parts per million, so the water must have 0.800 g of F⁻/ 1000000 g of the solution. The density of the water at room temperature is 997 kg/m³ = 997x10³ g/m³. So, the concentration of the fluoride will be:
0.800 g of F⁻/ 1000000 g of the solution * 997x10³ g/m³
0.7976 g/m³
The volume of the reservoir is the volume of the cylinder: area of the base * depth. The base is a circumference, which has an area:
A = πR², where R is the radius = 1.01x10² m (half of the diameter)
A = π*(1.01x10²)²
A = 32047 m²
The volume is then:
V = 32047 * 87.32
V = 2.7983x10⁶ m³
The mass of the F⁻ is the concentration multiplied by the volume:
m = 0.7976 * 2.7983x10⁶
m = 2.23x10⁶ g
