1. (Mon) A 2600 kg (5750lb) Escalade and a 1160 kg (2550lb) Cooper Mini are stopped at a stoplight. When the light turns green, and both accelerate to 20 m/s (45mph) in a distance of 300 m. How much less force did the Mini have to use to keep even with the Cadillac? (5 min / 5 pts)

2. W = Fd W = ΔKE W = KEf - KEi X Fd = ½mv² F = ½mv²/d ΔF = (½)(Δm)v²/d ΔF = (0.5)(2600kg-1160kg)(20m/s)²/(300m) ΔF = 960 N

3. (Tue) A roller coaster car loaded with people has a mass of 1000 kg. If the car at the top of the first hill has an initial ME of 1.031 MJ, and it drops 130 m on the first hill (30 m below the starting point) what is its speed when it reaches the bottom of the first drop (neglect friction)? (5 min / 5 pts)

4. 130 m 1.031 MJ MEi = MEf 1.031 MJ = ½mv² + mgh + ½kx² 1.031 MJ = ½(1000 kg)v² + (1000 kg)(9.81 m/s²)(-30 m) + 0 1.031 MJ = 500v² + (-294300 J) (1.031 MJ + 0.2943 MJ) / (500) = v² v² = 2650.6 m²/s² v = 51.48 m/s 30 m

5. (Wed) Quiz – No Warm Up Today

6. (Thu) A roller coaster car loaded with people has a mass of 1000 kg. Your car with a total ME of 1.031 MJ at the top of the first hill climbs from the first drop to the top of the second hill. If your speed at the top of the second hill is 32.88 m/s, how high above the starting point is the second hill (neglect friction)? (5 min / 5 pts)

7. 1.031 MJ ? m MEi = MEf 1.031 MJ = ½mv² + mgh + ½kx² (Thu) A roller coaster car loaded with people has a mass of 1000 kg. Your car with a total ME of 1.031 MJ at the top of the first hill climbs from the first drop to the top of the second hill. If your speed at the top of the second hill is 32.88 m/s, how high above the starting point is the second hill (neglect friction)? (5 min/5 pts) 1.031 MJ = ½(1000 kg)(32.88 m/s)² + (1000 kg)(9.81 m/s²)(h) 1.031 MJ = 540547.2 J + (9810 kgm/s²)(h) (1.031 MJ) – (540547.2 J) / (9810 kgm/s²) = h h = 50 m

8. (Fri) A 1000 kg elevator carries a max load of 800 kg. A constant friction force of 4000 N pulls down on the car as it goes up. What is the minimum power, in kW, that the motor must have to lift the car at 3 m/s? (10 min / 10 pts)

9. (Fir) A 1000 kg elevator carries a max load of 800 kg. A constant friction force of 4000 N pulls down on the car as it goes up. What is the minimum power, in kW, that the motor must have to lift the car at 3 m/s? (10 min / 10 pts) Fpull FgFf Mass = Mass Car + Mass People Mass = 1000 kg + 800 kg = 1800 kg Constant speed means Net Force =0 ΣFy = 0 or Fp = Ff + Fg Fp = 4000 N + (1800 kg)(9.81 m/s²) Fp = 21658 N P = W/t or P = Fv (use this one) P = (21658 N)(3 m/s) P = 64,974 W or…. P = 64.974 kW

10. End of Week Procedures 1.Add up all the points you got this week 2.Put the total number of points out of 25 points you earned at the top of your page (no total, lose 5 points) 3.List any dates you were absent or tardy (and why) 4.Make sure your name and period # is on the top of the page (no name, no credit) 5.Turn in your papers

11. (Wed) A 75 kg man jumps off of the roof of his garage 8 m above the ground and lands on his trampoline 1 m above the ground. If the total spring coefficient of the trampoline is 41 kN/m, how far does the trampoline flex down once he stops bouncing around? (5 min/5 pts)

12. At equilibrium: F net = 0 8m 1m ?m F g = F e or mg = kx (75kg)(9.81m/s²) = (41kN/m)(x) 735.75 N = 41,000(x) N x = 735.75 / 41,000 m x = 0.0179 m Or 1.79 cm (Wed) A 75 kg man jumps off of the roof of his garage 8 m above the ground and lands on his trampoline 1 m above the ground. If the total spring coefficient of the trampoline is 41 kN/m, how far does the trampoline flex down once he stops bouncing around? (5 min/5 pts)