♪

I'm Daisy from Design Squad. I'm with Eleanor and Reed. We're having fun with gravity. Gravity is present in all things. We use the invisible force of gravity to change the direction of speeding objects. NASA uses it too. When a spacecraft passes a moon or planet, they exert a gravitational pull on one another. NASA uses this to change the direction of a spacecraft, increase the speed or both-- change direction and increase speed.

This is called a gravity assist. Like gravity, magnets also exert an invisible force. We will use the invisible force of magnets to control how a ball rolls without touching the ball. We've got a steel marble, a magnet, a paper cup with a notch, an index card... folded to act as our ramp. This will be Mars. Let's put Mars maybe over here. We'll make this path, instead of going straight, curve like that. Let's place the magnet somewhere to alter the marble's course.

(Daisy) We have rope to keep the ball on the table. Maybe there. Yeah. Try it? Yep. The magnet didn't move the course of our steel ball. Maybe move this closer. So we don't want the ball to get too close to the magnet. That was close. That moved it a little. Try something with the magnet. The steel ball tends to get attracted towards the middle of the magnet. A little too close. We're getting there. There it goes! Wait. Try it again. There you go. Good job.

[laughing]

When the ball goes down the ramp, it always goes in a straight line, unless a different force acts against it to slow it or change its course. That's actually Newton's First Law. Let's change the direction of a rolling ball. The invisible force will be air coming from these leaf blowers. Ready? Goal!

[laughing]

(Daisy) For directions on this and more activities related to NASA, visit the Design Squad website. Eleanor, are you ready? Yes! Reed, are you ready? Yes!

Start your engines! [leaf blowers whirring]

And...go!

[whirring]