A bow has k = 458 N/m. It is pulled back 0.720 m, and used to fire a 0.0925 kg arrow. It hits a bird 24.7 m above the ground, What is the speed of the arrow when it hits? (Unit = m/s)

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

The ratio of lift to drag l/d for a wing or airfoil is an important aerodynamic parameter, indeed, it is a direct measure of the aerodynamic efficiency of the wing. if a wing is pitched through a range of angle of attack, l/d first increases, then goes through a maximum, and then decreases. consider an infinite wing with an naca 2412 airfoil. estimate the maximum value of l/d. assume that the reynolds number is 9x10^6.

What is the relationship between the direction of motion of the balloon and the wind currents