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Springs, Power and Friction

Springs, Power and Friction. Power. Friction. Springs. 10. 10. 10. 20. 20. 20. 30. 30. 30. 40. 40. 40. 50. 50. 50. Power – 10 Points. QUESTION: Your toaster uses 7200 Joules every hour and therefore has this power in Watts. ANSWER: What is 2 W?. Power – 20 Points.

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Springs, Power and Friction

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  1. Springs, Power and Friction

  2. Power Friction Springs 10 10 10 20 20 20 30 30 30 40 40 40 50 50 50

  3. Power – 10 Points • QUESTION: • Your toaster uses 7200 Joules every hour and therefore has this power in Watts. • ANSWER: • What is 2 W?

  4. Power – 20 Points • QUESTION: • You have four 50 W lightbulbs in your room. You study with them on for 2 hours a day for one week and use this much energy in kWh. • ANSWER: • What is 2.8 kWh?

  5. Power – 30 Points • QUESTION: • You want to lift a 900 kg elevator up 30 stories (120 m). The elevator needs to ascend at a rate of 5 seconds per story. You buy a motor with this many Watts of power. • ANSWER: • What is 7056 W?

  6. Power – 40 Points • QUESTION: • Your 1200 kg car is travelling 10 m/s and uses friction to stop over 5 s. Thermal energy is generated in this process with this power. • ANSWER: • What is 12000 W?

  7. Power – 50 Points • QUESTION: • You find a 10 m high waterfall where 1000 kg of water flow over it every second. If you set up a turbine to convert the water’s KE at the bottom of the waterfall into electricity, your turbine produces enough power to light this many 100-W lightbulbs. • ANSWER: • What is 980 lightbulbs?

  8. Friction – 10 Points • QUESTION: • Your 1000 kg car is travelling 5 m/s and then uses friction to stop. Friction did this much work in J. • ANSWER: • What is - 12500 J?

  9. Friction – 20 Points • QUESTION: • A 500 kg rollercoaster starts off on an 80 m high hill. If friction does -100,000 J of work between the first hill and the second, the second hill must be this high. • ANSWER: • What is 60 m?

  10. Friction – 30 Points • QUESTION: • A cross-country skier crosses a patch of snow with coefficient of friction = 0.1. If she starts off going 10 m/s, she travels this far along the snow before friction stops her. • ANSWER: • What is 51 m?

  11. Friction – 40 Points • QUESTION: • A 10-m tall grassy hill has a coefficient of friction of 0.15 and a slope of 30 degrees. A box moves this fast at the bottom of this hill. • ANSWER: • What is 12.0 m/s?

  12. Friction – 50 Points • QUESTION: • A 10 m tall grassy hill has a coefficient of friction of 0.12. If a box is moving 10 m/s at the bottom of the hill, the hill has this slope. • ANSWER: • What is 13.8 degrees?

  13. Springs – 10 Points • QUESTION: • A spring of spring constant k = 100 N/m is stretched 0.1 m. The spring stores this much spring potential energy. • ANSWER: • What is 0.5 J?

  14. Springs – 20 Points • QUESTION: • To store 50 J of PEs, a spring with spring constant k = 150 N/m is stretched this far. • ANSWER: • What is 0.82 m?

  15. Springs – 30 Points • QUESTION: • A spring with spring constant k = 40 N/m stores 100 J of energy. At that point, the spring pulls back with this much force in N. • ANSWER: • What is 89.4 N? (or -89.4 N if pulling down or left)

  16. Springs – 40 Points • QUESTION: • A bungee jumper of mass m = 50 kg falls 20 meters before the bungee stretches and 20 meters while it stretches. This is the bungee’s spring constant in N/m. • ANSWER: • What is 98 N/m?

  17. Springs – 50 Points • QUESTION: • A bungee jumper of mass m = 75 kg falls 20 meters before her bungee (of k = 56 N/m) stretches. She stretches the bungee this far. • ANSWER: • What is 24.3 m?

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