Poles, distance and a better gate

A farmer lets his cows and oxen eat in a big field in the day. At night they must be in the barn, where they are safe. But the barn gate opens like a door, and the animals have learned to push it open. How can we fix it? Engineers follow six steps: ask, imagine, plan, build, test and improve. First we ask what the problem is: the gate must stay shut when animals push, but the farmer must open it easily. Then each person imagines three ideas, such as a heavy bolt, a latch with a magnet on the gate and a steel plate on the post, or a gate that opens only inwards, into the barn, so that a push from inside presses it against the post. The team picks one idea and plans the tasks, who does each one, and a tick when it is done. To get new ideas, a team may take a toy apart with a grown-up, look at every part and what it does, and put the parts together in a new way. Next they build a model. Another team tests it and gives feedback: what works, and what must improve. A magnet latch pulls the gate shut, but a strong animal might push it open, so the team improves it with a second magnet or a hook. At the end they add up the cost of the materials with multiplication.