Answer:
c. Kinetic energy is conserved in all collisions .
Explanation:
the total kinetic energy of system of particles involved in the collision does changes .
kinetic energy is not conserved in all collisions because in some cases energy is converted to another form of energy that is heat etc .
Number of neutrons: atomic mass - atomic number
Element X's atomic mass is 79 and its atomic number is 39. Subtract 39 from 79 to find how many neutrons Element X has.
79 - 39 = 40
Element X has 40 neutrons.
Answer:
D. Hydrogen combines with oxygen to form water.
Explanation:
Hydrogen combining with oxygen to form water is a typical example of chemical reaction.
During a chemical reaction, atoms of elements are rearranged. Most chemical reactions obey the law of conservation of mass which states that "matter is neither created nor destroyed in a chemical reaction but atoms are simply rearranged".
The other choices given are nuclear reactions. In such reactions, atoms are not rearranged but are simply destroyed and made in the process.
When it comes to horizontal projectiles, the formula for time is:

Where:
dy = vertical distance or height
g = acceleration due to gravity
t = time
Based on the problem, we know that the height at which the tennis ball was thrown is 78.4 m and the acceleration due to gravity is a constant 9.8m/s2. All you need to do is input that into our equation:





The time it would take is
4 seconds.