D. J Ward

"Machines help make work easier, like when you need to lift something heavy or reach way up high. There are six simple machines: the lever, the wheel and axle, the pulley, the ramp, the wedge, and the screw. Can you adjust a seesaw to lift an elephant? What happens when you combine two or more simple machines? Read and find out!" --

"Millions of people live in cities around the world, but have you ever wondered how cities work? All those people need clean water to drink, a safe place to live, and a way to get all around the city! How do you take care of all those people's needs? Your city has a plan for that. Read and find out all about the systems a city has to help keep everyone safe, healthy, and happy." --