Q.1 The plank (see the Figure below) is a great way to strengthen abdominal, back, and shoulder muscles. The mass of this athlete is 75kg and its height is 1.80 m tall. In plank position the distance from his toes to the middle of his forearms is 1.53 m and its centre of mass is 1.30m far from his toes. Find the reaction forces exerted on this athlete by the ground. (7 marks)
