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Radda [10]
3 years ago
10

A 72.9 kg man stands on a spring scale in an elevator. Starting from rest, the elevator ascends, attaining its maximum speed of

1.21 m/s in 0.80 s. It travels with this constant speed for 4.97 s, undergoes a uniform downward acceleration for 1.52 s, and comes to rest. What does the spring scale register (a) before the elevator starts to move?
Physics
1 answer:
andrew-mc [135]3 years ago
8 0

Answer:

(a) 72.9 kg

Explanation:

Before the elevator starts to move, only gravitational force exerts on the man, this force is generated by the man mass and the gravitational acceleration, which in turn register in the scale. So the scale would probably indicate the man mass, which is 72.9 kg.

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If an atom has 15 protons, 12 neutrons, and 17 electrons, what is the atom's electrical charge? A. -5 B. -2 C. +3 D. +5
Nimfa-mama [501]

Answer:

B. -2

Explanation:

The total charge on an atom is the sum of all individual charges present in it. Therefore, the total charge on this atom is given by the following formula:

q = (n_p)(q_p)+(n_e)(q_e)+(n_n)(q_n)

where,

q = total charge on atom = ?

n_p = no. of protons in the atom = 15

n_e = no. of electrons in the atom = 17

n_n = no. of neutrons in the atom = 12

q_p = charge on proton = +1

q_e = charge on electron = -1

q_n = charge on neutron = 0

Therefore,

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Hence the correct option is:

<u>B. -2</u>

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klasskru [66]

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