<span>A pure substance is an element or compound. If it's an element, then it's made of only one kind of atom. If it's a compound, then it's made of only one kind of formula unit. For example, hydrogen (H2) and oxygen (O2) are elements. In pure samples of H2 and O2, you find only one kind of element. H2O is a compound, water. In pure samples of H2O, you find only formula units of H2O (called molecules because H2O is covalent). Neither the components that make up H and O atoms, nor the atoms that make up H2O can be separated by physical means. H2, O2, and H2O are all considered substances. </span>
Answer:
The correct answer is the third
Force equals mass times acceleration
Explanation:
Newton's second law says that force equals mass times the acceleration of the body
F = m a
This is the most used way to solve problems
The correct answer is the third
Newton's third law states that forces always work in pairs, by action and reaction
Newton's first law states that an object per macerate with constant speed unless some force modifies this state.
Answer:
The speed with which the pebble strikes the ground is 30.4m/s
Explanation:
Initial velocity (u) = 17.5m/s, height (h) = 31.5m, acceleration due to gravity (g) = 9.8m/s^2
V^2 = u^2 + 2gh = 17.5^2 + 2×9.8×31.5 = 306.25 + 617.4 = 923.65
V^2 = 923.65
V = √923.65 = 30.4m/s
Answer:
c. 43 m/s
Explanation:
Given the following data;
Displacement, S = 90 meters
Time, t = 5.55 seconds
To find the initial velocity;
We would use the second equation of motion given by the formula;

Where;
- S represents the displacement or height measured in meters.
- u represents the initial velocity measured in meters per seconds.
- t represents the time measured in seconds.
- a represents acceleration measured in meters per seconds square.
We know that acceleration due to gravity is -9.8m/s² because the direction is downward.
Substituting into the equation, we have;



Rearranging the equation, we have;



Initial velocity, u = 43.41 ≈ 41 m/s