#### Practice problems for the first test

1. Joe has a regular 9-5 job at the grocery store. He realizes one day as he checks his bank account, "Hey, I've been working at this store for exactly one calendar month, and my total pay so far comes to, oh, something between \$800 and \$900."

1. What is Joe's average wage, in dollars per hour? Include an uncertainty.
2. Frosty the Snowman is riding on his toboggan across the snowy landscape. Just as he reaches the base of a hill, his speed is v0 = 9 m/s. Frosty slides up a very uniform slope, gradually slowing down, until he comes to a momentary halt exactly L = 20 meters along the slope from the bottom.

1. If there is no friction between the sled and the hill, what is the angle of the hill?
2. If the coefficient of kinetic friction between the hill and the sled is μk = 0.05 , what is the angle of the hill?
3. Nasty Ned grabs the kickball from some second-grade kids at recess. He kicks the ball with an initial velocity of v = 25 m/s at theta = 28 degrees above the horizontal. The ball rises up into the air and lands on the roof of the gymnasium, H = 3 meters above the playground.

1. How long was the ball in the air?
2. What was the velocity of the ball just before it landed on the roof?
3. How far from Ned is the ball when it lands?
4. Crazy Ellie is piloting the Virgin Galactic Space Plane as it coasts from Earth to Mars. The initial velocity of the M = 26 tonne craft is v0 = 15 km/s, directly toward Mars. The ship is exactly on schedule to reach its destination at 2:00 PM tomorrow, in exactly 10 hours.

Exhausted by last night's party, Ellie falls asleep. Her elbow pushes the thrust-control button, causing the engines to push the ship back toward Earth with a constant force of 500 kiloNewtons. Two minutes later, she jerks awake and sits up, turning the engines off.

1. What is the velocity of the ship now?
2. How many miles behind schedule is the ship now?
3. If the ship continues to travel toward Mars with its current velocity, when will it arrive at the destination?