Тіло піднімають похилою площиною, прикладаючи в напрямку руху тіла силу 50 Н. Визначте масу тіла, якщо довжина похилої площини дорівнює 2 м, її висота — 50 см, а ККД становить 80 %.

My best friend is (имя), He/she is slim and not very tall. He/she  has a brown hair and blue eyes. In my opinion he/she is cute. My friend is intelligent, cheerful, good-tempered and sporty.He/she is very good at math and bascetball .
We became friends since 1 class. We spend a lot of time together. We chatting, walking and do another things for fun. Also we often play bascetball and volleyball with our friends. We love the same music, films and poits of view. When I fell upset my mate always cheer me up. I do the same for him/her. My friend is very reliable and always helps me in different situations.