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Physics Exam Review – Science 10 1. Define heat and temperature Heat: Transfer of thermal energy from one object to another Temperature: average kinetic energy if the particles in a substance 2. Write (in your own words) the first and second law of thermodynamics. First law: energy cannot be created or destroyed Second Law: No process (energy conversion) can be 100% efficient. Some energy is always lost as heat 3. Fill in the following chart: Quantity Scalar/Vector? Work Vector Distance Scalar Units J Formula W = Fd W d m, cm, etc. d = d1 + d2… Vector D m, cm, etc. d = d 2 – d1 m/s v = d/t Velocity Scalar Vector v v m/s v = (d2-d1)/t Acceleration Vector a m/s2 a =( v2 – v1)/t Displacement Symbol Speed 4. Solve the following problems. Remember to round to the correct number of significant digits! a. How much work is done lifting a book 2.0 m with 45 N of force? =90 J b. A horse runs 100 m (South) in 8.0 s. What was its velocity? = 13 m/s, south c. You walk 15.0 m North and then 2.5 m south in 120 s. What was your displacement AND speed? d = 12.5 m, North v = 0.15 m/s 1 d. A car reaches a velocity of 100 m/s in 9 s. What was the car’s acceleration? = 1 x 101 m/s 5. Fill in the following chart: Quantity Definition Kinetic Energy Energy of motion Potential Energy Stored energy Efficiency how efficient a system is at converting energy from one form to another Symbol Ek Units J Formula Ek = ½ mv2 Ep J Ep = mgh e None: it’s a ratio (percent) = output/input x 100 6. Solve the following problems. Remember to round to the correct sig digs! a. What is the kinetic energy of a 1000 kg car moving at 13 m/s? = 8.5 x 104 J b. A 0.30 kg baseball has 54 J of energy. What is its speed? = 19 m/s c. How much potential energy does a 0.50 kg book have sitting on a shelf 3.0 m high? = 15 J d. You drop a penny from a 150 m tall building. What is its speed at the bottom? = 54.2 m 2 e. An electrical generator uses 50 J of energy to produce 2 J of electricity. Calculate the efficiency. =4% f. You are pushing a box filled with books across a floor. If you did 322.5 J of work by pushing the box a distance of 4.3 m, what force did you exert? = 75 N g. Homer’s car broke down, and he needs to push it home to Evergreen Terrence. If he pushed the car 570 m, with a force of 780 N, how much work did he do? = 4.45 x 105 J h. On a recent trip to Africa, you have a ticked off a baby hippopotamus, and it starts to run at you with a speed of 12 m/s. If the hippopotamus has a mass of 780 kg, what is it’s kinetic energy? = 5.6 x 104 J i. A 15 kg child is sliding down a playground slide. If the child’s kinetic energy is 77 J, how fast is the child sliding? = 3.2 m/s 3 j. A mountain lion is sitting in a tree 7.5 m above the ground. If the mountain lion has a mass of 545 kg, what is it’s gravitational potential energy? = 4.0 x 104 J k. A boulder rests on a ledge 36 m above a lake. If it has 2.8 x 105 J of potential energy relative to the lake surface, what is the mass of the boulder? If it falls, what will be its velocity as it hits the water? = 7.9 x 102 kg l. 4500 N of force is required to stop a car with a mass of 1600 kg. If the car is traveling at a speed of 15 m/s, what is it’s stop distance? = 40 m m. A roller coaster raises its passengers a vertical distance of 42.1 m above the ground. If the total mass of the coaster and passengers is 5.27 x 103 kg, what is … a. The gravitational potential energy? = 2.18 x 106 J 4 b. The speed of the roller coaster once it drops? = 28.7 m/s n. Name three types of potential energy. Chemical, elastic, gravitational, nuclear 5