CHAPTER ONE PLAY BALL and his friends were playing catch in the it was a sunny summer afternoon Alex backyard Everyone was standing far apart They liked the challenge of throwing the ball as far as they could Alex threw the baseball to Jack He tossed it high into the air He had to throw it hard so it would reach Jack It curved through the air It landed in Jack’s glove Jack turned quickly and A game of catch can be a fun form of exercise 5
threw the ball as hard as he could to Priya It went so fast that Priya had to act quickly to catch it They kept playing for a long time Sometimes they missed the ball It fell to the ground or whizzed past the catcher’s shoulder When they got tired they moved closer together They gently tossed the ball to each other They didn’t have to throw as hard for the ball to reach the person catching It still followed a curved path through the air with each throw FRESH AIR Playing in the backyard or at the park can have health benefits Sunlight helps the body produce vitamin D The human body needs this vitamin in order to absorb calcium Calcium is a mineral found in foods It helps build healthy bones Vitamin D can also help prevent health issues such as cancer and bone problems Being outside increases physical activity Both sunlight and exercise improve people’s moods Spending time outdoors can even help people concentrate better 6
A GAME OF CATCH The basic process of a game of catch is very simple One person throws a ball to another person That person catches the ball and throws it back The different forces that make the ball move are more complicated Forces affect the motion of an object They cause an object to start moving stop moving or change its movement A girl may be throwing a ball to her brother She pulls her arm back while holding the ball Then her arm muscles move her arm and the ball forward quickly This action produces a force on the ball It sets the ball in motion When she lets go of the ball the girl is no longer putting any force on it But the throw did give the ball its starting velocity Velocity is the speed of an object combined with the direction in which the object is moving The ball has vertical velocity This is the speed at which the ball is moving up or down The ball also has horizontal velocity This is the speed at 7
