Calculate the force required to hold a water hose of radius 0.04 m when it emits a jet of water at a speed of 20 m/s.

# Newton’s Laws

# Jar of Flies

A scientist weighs a jar of sleeping flies. Then, he shakes the jar to wake them up. While flies are flying in a closed jar, the scientist weighs the jar again. Does the jar weigh less when the flies are flying?

# How long would it take to fall through the center of the Earth?

# What is the surface temperature of the planet?

# Object, String & Elevator

An object of mass m is hanging by a string from the ceiling of an elevator. The elevator is moving upward, but slowing down.

What is the tension in the string?

a) zero

b) greater than mg

c) exactly mg

d) less than mg

# If the solar system were reduced

If all the linear dimensions of the solar system were reduced in some proportion, then what will be the length of Earth’s year?