You need a windy day. Bundle the kids up according to the weather/temperature, and take the parachute. Give each kid a handle to hold with two hands, and wait for the wind to blow. Have the kids flap their arms up and down, in a silly way for a moment or two while you're waiting for the wind to blow. Then the parachute will take on a life of its own. The wind will zoom around, pushing the parachute UP or DOWN, which is good for demonstrating the FORCE of the wind, and they can also see the VELOCITY as the parachute snaps up or down with the wind gusts. On a really strong gust, have the kids bend forward so that the parachute is almost touching the ground. While the wind is blowing, have the kids TRY to raise their arms up. If the wind is strong enough, they WILL NOT be able to raise the parachute off the ground, and it will flatten out into a bowl... On the next powerful gust, have the kids raise their arms. The wind will go under the parachute, and cause it to billow, causing it to look like a jellyfish. Have the kids try to pull it down. This is less difficult than raising it... They find this experiment interesting and exciting because the wind is "invisible" and it is stronger than they are!