A firefighter sprays water out of a fire hose onto a burning house.
1. As water sprays out of the hose, the firefighter must hold on tight and be sure that his feet are firmly planted. How does the force exerted on the fireman by the spraying water depend on the velocity of the water that leaves the hose?
2. His feet suddenly loose traction and he begins to slide backward away from the burning house. Neglecting any air resistance as he moves back will he move at constant speed? If not, how will his speed change?
3. The valve on the nozzle is stuck open so that he can't stop the spraying water. Is there a way he can stop himself from sliding using the spraying water? How?
4. Not realizing how to stop himself from sliding he continues to slide backward with the water spraying toward the fire until his heels suddenly encounter a curb. When his feet suddenly stop moving he will very likely end up on his back. Why?
5. If he lets go of the hose it will not continue to move straight back away from the fire, but instead will flail about wildly. Why?
A salad spinner is a clever device designed to dry lettuce. It consists of a basket inside a bowl with a lid. The lid has a handle on top, which when rotated spins the basket and lettuce inside.
6. The crank on top turns a gear, which is connected to a gear that turns the basket. As the crank is turned slowly by hand the basket spins rapidly. How do the sizes of the gears connected to the crank and to the basket compare?
7. Instead of a crank some salad spinners have a string which is pulled to spin the basket. After the string is pulled the basket keeps spinning without winding up the string. How is this accomplished?
8. Eventually the basket will stop spinning, but to stop it faster you can tip the spinner so that the basket rubs against the wall of the bowl. How does this stop the basket sooner?