4. a freight elevator is used to lift loads of 12,000 n at a vertical distance of 250 m. the elevator takes…
4. a freight elevator is used to lift loads of 12,000 n at a vertical distance of 250 m. the elevator takes 10 s to make this trip. assuming no energy loss, what is the average power expenditure of the elevator when working? (a) 300,000 w (b) 3,000,000 w (c) 12,000,000 w (d) 30,000,000 w 5. the air in the troposphere is made up primarily of: (a) oxygen (b) helium (c) carbon dioxide (d) nitrogen 6. the cell membrane that surrounds an animal cell is a (a) non - permeable structure (b) semi - permeable structure (c) fully permeable structure (d) cell wall 7. at which level of the atmosphere does all weather (a) troposphere (b) stratosphere
Answer
4.
Explanation:
Step1: Calculate work done
Work (W = F\times d), where (F = 12000\ N) and (d=250\ m). So (W=12000\times250 = 3000000\ J).
Step2: Calculate average power
Power (P=\frac{W}{t}), with (W = 3000000\ J) and (t = 10\ s). So (P=\frac{3000000}{10}=300000\ W).
Answer:
A. 300,000 W
5.
Brief Explanations:
The air in the troposphere is composed mainly of nitrogen (about 78%).
Answer:
D. nitrogen
6.
Brief Explanations:
The cell - membrane of an animal cell is semi - permeable, allowing certain substances to pass through while restricting others.
Answer:
B. semi - permeable structure
7.
Brief Explanations:
All weather occurs in the troposphere, which is the lowest layer of the atmosphere.
Answer:
A. troposphere