Автомобиль массой 1т движется со скоростью 20 м/с. Определить его импульс.

Автомобиль начинает движение из состояния покоя так, что за каждые 2 с увеличивает скорость на 4 м/с. Определить ускорение автомобиля.

1)[tex](1905 * 690 - 2006 * 607 + 39872) : 402 - 284 = ?[/tex]Помогите пожалуйста!Решите по действиям!

2)Мама купила 2 кг яблок по цене 45 руб. за килорамм и в 3 раза больше помидоров по цене 9 руб.больше, чем цена яблок.Сколько сдачи она должна получить с 500 рублей?

Пожалуйста!Кому не трудно,решите эти упражнения! 

Выберите правильный вариант: 1. Liz and I are good friends. We know/have known each other for four years. 2. Sarah is very tired. She has been working/is working hard all day. 3. “Where is John?” “He’s upstairs. He does/is doing his homework”. 4. I can’t go to the party on Saturday. I am leaving/have been leaving for Spain on Friday night. 5. Jane has finished/is finishing cleaning her room, and now she is going out with her friends. 6. I didn’t recognise Tom. He looks/is looking so different in a suit. 7. I don’t need to wash my car. Jim washes/has washed it for me already. 8. Ian has been talking/is talking to his boss for an hour now? 9. Claire’s train arrives/has arrived at 3 o’clock. I must go and meet her at the station. 10. “Would you like to borrow this book?” “No, thanks. I have read/have been reading it before”. 11. “Where are you going/do you go?” “To the cinema. Would you like to come with me?” 12. Have you seen my bag? I am searching/have been searching for it all morning. 13. “Is Colin here?” “I don’t know. I haven’t seen/haven’t been seeing him all day”. 14. Sophie is very clever. She is speaking/speaks seven different languages. 15. We are moving/have moved house tomorrow. Everything is packed.