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4. a 20-kg child is tossed up into the air by her parent. the child is 2 meters off the ground traveling 5 m/s.

circle one: ke / gpe / both

show your work for finding the values of each type of energy the object has:

both

KE = 250 J

PE = 392 J

Explanation:

Given that the child started resting, then after he was tossed up, he gained both, gravitational potential energy (now is in a higher position) and kinetic energy (his speed increase from 0 to 5 m/s).

Kinetic energy is calculated as follows:

KE = (1/2)*m*v^2

where m is mass and v is speed. Using mass in kg and speed in m/s, KE is in J.

KE = (1/2)*20*5^2 = 250 J

Gravitational potential energy is calculated as follows:

GPE = m*g*h

where g is the standard acceleration due to gravity = 9.8 m/(s^2) and h is height. Using mass in kg, g in m/(s^2), and h in m, GPE is in J.

GPE = 20*9.8*2 = 392 J

the equation that correctly represent the reaction for formation of ammonia is

n2+ 3h2 → 2nh3 (answer d)

1 mole of nitrogen gas (n2) react with 3 moles of hydrogen gas (h2) to form 2 moles of ammonia ( nh3). this is in a process known as haber process were iron is used as a catalyst and reaction take place that a higher temperature and pressure. the process is exothermic hence energy is released.

answer: -

reaction:

na + cl ⇌ nacl

balanced chemical equation:

na + 2cl ⇌ nacl2

sodium + clorine goes to form sodium chloride (table salt).

the product is nacl2.

and the reactants are na and cl.

(note: if you don’t know what ⇌ means, read below: -

⇌(double head arrow) means reversible reaction).