Let's address each question one by one:
37. The table shows the times it took different animals to cover various distances.
To find the speed of each animal, we can use the formula:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]
Now, let's calculate the speed for each animal:
-
Gray fox:
- Distance = 73 km, Time = 1.05 h
- Speed = \( \frac{73}{1.05} \approx 69.52 \) km/h
-
Cheetah:
- Distance = 85 km, Time = 0.75 h
- Speed = \( \frac{85}{0.75} \approx 113.33 \) km/h
-
Gazelle:
- Distance = 68 km, Time = 0.85 h
- Speed = \( \frac{68}{0.85} \approx 80.00 \) km/h
-
Rabbit:
- Distance = 70 km, Time = 1.25 h
- Speed = \( \frac{70}{1.25} \approx 56.00 \) km/h
Now we compare the speeds:
- Gray fox: 69.52 km/h
- Cheetah: 113.33 km/h
- Gazelle: 80.00 km/h
- Rabbit: 56.00 km/h
The greatest speed is that of the Cheetah (113.33 km/h).
Answer: B) cheetah
38. Which scenario best demonstrates an example of Newton's first law of motion?
Newton's first law states that an object at rest stays at rest, and an object in motion stays in motion unless acted upon by a net external force.
The best example is:
c) A car passenger moves forward when a car suddenly stops.
This demonstrates Newton's first law because the passenger continues in motion due to inertia until a force (the seatbelt, for example) acts on them.
Answer: c) A car passenger moves forward when a car suddenly stops.
39. A radioisotope has a half-life of 7.5 hours. How many half-lives have occurred after 67.5 hours?
To find the number of half-lives that have occurred, we divide the total time by the half-life:
\[ \frac{67.5 \text{ hours}}{7.5 \text{ hours/half-life}} = 9 \text{ half-lives} \]
Answer: c) 9 half-lives
40. Column A (the solubility scenarios) and Column B (solubility conditions):
To classify the given amounts of solutes with respect to their saturation level:
-
20g of NaCl at 50°C
- Generally, NaCl is soluble in water. This amount would likely be unsaturated, as 20g is typically below the saturation point at 50°C.
-
45g KCl at 60°C
- KCl’s solubility increases with temperature. 45g may be near or below the saturation limit at 60°C, depending on specific solubility data. Generally considered unsaturated but could be close to saturated.
-
70g of CaCl2 at 10°C
- Calcium chloride is very soluble, and at 10°C, 70g would likely saturate or exceed most solubility limits. This is typically considered supersaturated if dissolved.
Based on the data, we classify them:
1 → a. unsaturated
2 → a. unsaturated (or close to saturated, but typically unsaturated)
3 → b. supersaturated
Answer: 1a, 2a, 3b (depending on detailed solubility data)
Let me know if you need additional information or clarifications!