| 1. | upward, upward | 2. | upward, downward |
| 3. | downward, upward | 4. | downward, downward |

| 1. | \(25\) N | 2. | \(39\) N |
| 3. | \(6\) N | 4. | \(10\) N |
| Statement I: | When a railway engine pulls a train and the system moves forward, the force exerted by the engine on the train is greater than that exerted by the train on the engine. |
| Statement II: | The normal force exerted by the ground on a man is the reaction force of the weight of the man. |
| 1. | Statement I is incorrect and Statement II is correct. |
| 2. | Both Statement I and Statement II are correct. |
| 3. | Both Statement I and Statement II are incorrect. |
| 4. | Statement I is correct and Statement II is incorrect. |
| 1. | \(4\) | 2. | \(3\) |
| 3. | \(2\) | 4. | \(1\) |

| 1. | \(80~\text{N}\) | 2. | \(60~\text{N}\) |
| 3. | \(40~\text{N}\) | 4. | \(100~\text{N}\) |
