Answer:
density d = 1.59 g/cm^3
The density of the rock is 1.59 g/cm^3
Explanation:
The density of an object can be derived by measuring its mass and then measuring its volume by submerging it in a graduated cylinder.
Density = mass/volume of water displaced
d = m/v ........1
Given;
mass m = 344 g
Volume of water displaced v = 216 cm^3
from equation 1, we can calculate the value of the density;
Substituting the given values;
d = 344/216 g/cm^3
d = 1.592592592592 g/cm^3
d = 1.59 g/cm^3
The density of the rock is 1.59 g/cm^3
Complete question is;
Shoveling snow can be extremely taxing since the arms have such a low efficiency in this activity. Suppose a person shoveling a sidewalk metabolizes food at the rate of 800 W. (The efficiency of a person shoveling is 3%.)
(a) What is her useful power output? (b) How long will it take her to lift 3000 kg of snow 1.20 m? (This could be the amount of heavy snow on 20 m of footpath.) (c) How much waste heat transfer in kilojoules will she generate in the process?
Answer:
A) P_out = 24 W
B) t = 1470 s
C) Q = 1140.72 KJ
Explanation:
We are given;
Input Power; P_in = 800 W
Efficiency; η = 3% = 0.03
A) Formula for efficiency is;
η = P_out/P_in
Making P_out the subject, we have;
P_out = η•P_in
P_out = 0.03 × 800
P_out = 24 W
B) We know that;
Power = work done/time taken
Thus;
P_out = mgh/t
We are given;
m = 3000 kg
h = 1.20 m
Thus, time is;
t = (3000 × 9.8 × 1.2)/24
t = 1470 s
C) amount of heat wasted is calculated from;
Q = (P_in - P_out)t
Q = (800 - 24) × 1470
Q = 1,140,720 J
Q = 1140.72 KJ
B. The number of coils of wire around the core
Answer:
NaNO3.
Explanation:
The Na ion has one positive charge and the NO3 ion has one negative charge so the correct formula is NaNO3.
