Question

1. As a demonstration of lab safety violations, a stainless steel water bottle is filled with a small amount of liquid nitrogen, and then the cap is sealed on the bottle (don’t ever do this – you could get seriously hurt). The bottle is laid on its side on the edge of the roof of the library building, which is 14 meters above the street below. When the bottle explodes, the 240 gram bottle flies back onto the roof and you measure its initial velocity to be 6.1 m/s. You can clearly see this velocity is initially completely horizontal. The 20.0 gram cap flies off the roof also with an initial velocity that is completely horizontal. How far away from the edge of the building does the cap land? You can assume air resistance is negligible.

2. You get a summer job testing springs at a manufacturing plant. Every 50th spring is taken off the line and is pushed with a force sensor a certain distance to make sure the spring constant is within specifications. The force sensor quits working. You devise a method using a flat track to push a 500 gram calibration mass along the track and then up a ramp angled at 20°. You cover the ramp and track with lubrication to make it nearly frictionless, but run out before you can coat the entire thing, leaving a 25 cm length on the flat part of the track with friction. Using a spring with a known spring constant of 150 N/m, you compress the spring 10 cm with the mass. You release the mass and measure it to go 23.0 cm along the angled part of the ramp when it stops. (a) What is the coefficient of friction of the patch left unlubricated? (b) If the springs you are currently manufacturing are supposed to be 400 N/m constants and you compress it 5 cm with the calibration mass, how far along the angled ramp should the calibration mass slide, assuming the friction is still present?

3. You set up a small ramp in your house to do some physics experiments. It is a smooth metal sheet and you are using an ice cube as a way to slide without friction. Your sheet is 1.42 meters long and you prop it up at an angle of 27°. You make a large ice cube of 250 grams for your experiment. a. If you allow the ice cube to slide from the top of the ramp, how fast is it going at the bottom? b. If the ice cube falls off the top of the ramp over the edge (instead of sliding down the ramp), how fast is it going when it hits the ground? c. If you wanted to slide the cube from the bottom of the ramp to the top, how much work would you do pushing it, assuming the speed at the bottom of the ramp and top of the ramp is zero? d. How much work does gravity do during the push from part (c)?

Answer 1