2. Final Jeopardy Question Final Jeopardy Question Final Jeopardy Question Final Jeopardy Question Momentum 500 100 200 300 400 Forces 500 400 300 200 100 Energy 500 400 300 200 100 Electricity 100 200 300 400 500

3. A 20kg car moving 5m/s to the right crashes into a 45kg truck moving 10m/s to the left. Afterwards the truck is moving 4m/s to the right. Which direction and how fast is the car moving? Back 20kg*5m/s + 45kg(-10m/s) = 45kg*4m/s + 20kg*v 100kg*m/s – 450kg*m/s = 180kg*m/s + 20kg*v -350kg*m/s = 180kg*m/s + 20kg*v -530kg*m/s = 20kg*v V = (-530kg*m/s)/20kg = -26.5m/s

4. If a 20kg truck moving 15m/s to the right crashes into a 5kg car moving 20m/s to the left and they stick together, which direction and how quickly do they move? 20kg*15m/s + 5kg(-20m/s) = (20kg + 5kg) v 300 kg*m/s – 100 kg*m/s = 25kg * v 200 kg*m/s = 25kg*v V = 8 m/s to the right Back

5. A 30kg truck is moving 5m/s to the right when it crashes into a 10kg car at rest. If the car moves 10m/s to the right, which direction and how fast does the truck move? 30kg*5m/s = 30kg*v + 10kg*10m/s 150kg*m/s = 30kg*v + 100kg*m/s 50kg*m/s = 30kg*v V = 1.6m/s Back

6. 20kg*4m/s = 5kg*v 80kg*m/s = 5kg*v v=16m/s A 20kg truck moving 4m/s crashes into a 5kg car at rest. If the truck stops, how fast does the car move? Back

7. How much momentum does a 35kg car moving 14m/s have? 35kg*14m/s = 490 kg*m/s Back

8. If a 20kg ball is compressed 4m in a spring (k=1000N/m) and released, how fast will it move when it is 5m in the air? SPE before = ½ 1000N/m * (4m) 2 =500N/m*16m 2 = 8000J Total Energy After = 8000J GPE + KE after = 8000J 20kg*10m/s/s*5m + 1/2*20kg*v 2 =8000J 1000J + 10kg*v 2 = 8000J V 2 = 700m 2 /s 2 ; v = sqrt 700 m/s Back

9. If a 10kg ball is moving 5m/s down when it is 10m high, how far will it compress a spring (k=200N/m) if 225J are lost as friction KE+ GPE - Friction → SPE 1/2*10kg*(5m/s) 2 + 10kg*10m/s/s*10m - 225J = SPE 125J + 1000J -225J =1/2(200N/m)x 2 900J= 100N/m *x 2 9m 2 = x 2 ; x=3m Back

10. How much force is required to stop a 10kg car Moving 4m/s in 4m W=ΔKE; KE = ½ *10kg(4m/s) 2 W = 80J = F*4m F=20N Back

11. How fast would a 10kg sled on top of a 8m hill move when it reaches the bottom? GPE → KE 10kg*10m/s/s*8m → ½ 10kg v 2 800J → 5kg * v 2 160m 2 /s 2 --> v 2 v=sqrt 160 m/s Back

12. How much kinetic energy does a 20kg car moving 15m/s have? ½ 20kg*(15m/s) 2 = 2250J Back

13. A 75kg man is accelerating down 2m/s/s On an elevator. What will a scale say he weighs? Net force = 75kg*2m/s/s = 150N down Fg = 75kg*10m/s/s = 750N down F up = 600N = reading on scale Back

14. A 10kg object is being pulled by a spring (k=100N/m) that is causing it to accelerate up at 5m/s/s. How far is the spring stretched? Fnet= 5m/s/s*10kg = 50N up Fdown = 100N, Fup = 150N 100N/m * x = 150N x=1.5m Back

15. Fup =800N, Fdown =500N, net force = 300N up A=Fnet/m = 300N/50kg = 6m/s/s up A 50kg person riding an elevator is on a scale. It says he weighs 800N. Which direction are They accelerating and at what rate Back

16. A 20kg object is hanging from a spring (k=20N/m). How far does it stretch? Fdown=200N, Fup =200n 200N = 20N/m * x X=10m Back

17. Draw a free body diagram of a 100kg car driving 10m/s if there is 100N worth of friction. Fup+down = 1000N Fleft+right = 100N Back

18. No, they are both positively charged An atom with 8 protons, 7neutrons and 7 electrons is near an atom with 9 protons, 9 neutrons and 7 electrons. Are they attracted to each other? Back

19. Draw an atom. Label the protons, neutrons and electrons Back

20. An object with charge -6 is near an object with charge +2. What are their final charges and why? -2,-2. 4 electrons flow Back

21. 180N * 1/9 = 20N The electric force between two objects is 180N. If they are 3x as far apart, what is the force? Back

22. What part of the atom carries negative charge? Positive charge? Electrons, protons Back

23. Identify as many units as you can (include what variable they go with) 100pts/unit Distance-mVoltage - volts Velocity –m/sCurrent - amps Acceleration-m/s/sWattage- watts Time-sCharge - coulombs Force –NSpring Cons. - N/m Energy – J Momentum – kg*m/s Back