Q1. Two horizontal forces, 231N and 190N, are exerted in opposite directions on a crate. What is the net horizontal force on the create? Be sure to indicate the direction of the net force. (Assume that the 231 N forces are in the positive direction.)

Q2. A clean copper surface is exposed to light of wavelength 275 nm. What is the maximum speed of the photoelectrons emitted from this surface? Use the table below copper=4.7eV

Q3. A winter hiker's body generates heat at a rate up to a maximum value of 126 W. She is hiking on a brisk day in which the outdoor temperature is 9 °C, while wearing a jacket with goose down insulation. How thick should jacket be so that she can maintain a normal body temperature? Suppose her surface area for heat flow (the jacket) is 1.50 m2 and that all of her body heat flows out through the jacket. (Assume the thermal conductivity to be 0.025 W/m • K.)