PS 300 extra credit for exam 1 (5% max) due 2/13/18

Transcription

1 PS 300 extra credit for exam 1 (5% max) due 2/13/18 Name: 1. Name three physical properties that describes an object: mass, temperature, density, volume. 2. What is the mass of gasoline (ρ = g/cm 3 ) in a 14.6 L gasoline tank? Volume = 14.6L = 14600ml= cm 3 mass= ρ x V = (ρ = g/cm 3 ) (14600 cm 3 )=9928 g 3. What unbalanced force is required to accelerate a 1500 kg race car at 3.00 m/s 2? 4. When a shot putter exerts a net force of 140 N on a shot, the shot has an acceleration of 19 m/s 2. What is the mass of the shot. 5. A 7.3 kg bowling ball sliding down a smooth ramp has a net force of 20 N exerted on it. What is its acceleration? 6. Together a motorbike and rider have a mass of 275 kg. The rider slows the motorbike at 4.5 m/s 2. What is the net force on the motorbike? What does the negative sign signify? 7. A towrope is used to pull a 1750kg car, giving it an acceleration of 1.35 m/s/s. What force does the rope exert? 8. What is the net force acting on the following object? If the mass of the object is 2.0kg, what are their accelerations? 5N 12 N

2 9. Find the net force acting on the object. 48 N 21 N 10. You weigh a bear by making him stand on four scales as shown. Draw a free-body diagram showing all the forces acting on the bear. If his weight is 1,500 newtons, what is the reading on the fourth scale? 11. A runner has a mass of 89 kilograms. He produces a force of 84 Newtons between the ground and his running shoes. How fast does he accelerate? 12. Calculate the acceleration of a car if the force on the car is 450 Newtons and the mass is 1300 kilograms. 13. State which of Newton s Three Laws best applies to the following situations: a) A rock falls off a cliff, and accelerates towards the ground. b) Two physics students give each other a high five. Their hands hurt! c) A car is stuck in the snow, spinning its wheels trying to move forward.

3 14. Fill the blank All objects will remain at, or will continue to move at a constant in the same unless acted upon by an unbalanced. This property is called. 15. Unbalanced forces cause an object to. This can be stated mathematically by the formula: 16. Every action produces an equal and opposite. When one object exerts a force on another object, the second object pushes back with the same amount of. 17. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. What will the rock do? Why? 18. Why doesn t a ball roll on forever after being kicked at a soccer game? 19. Ben Too close is being chased through the woods by a bull moose which he was attempting to photograph. The enormous mass of the bull moose is extremely intimidating. Yet, if Ben makes a zigzag pattern through the woods, he will be able to use the large mass of the moose to his own advantage. Explain this in terms of inertia and Newton's first law of motion. 20. Luke Autbeloe drops an approximately 5.0 kg object (weight = 50.0 N) off the roof of his house into the swimming pool below. Upon encountering the pool, the object encounters a 50.0 N upward resistance force (assumed to be constant). Use this description to answer the following questions. (Down is usually considered a negative direction) a) Which one of the velocity-time graphs best describes the motion of the object? Why?

4 b) True or False: Once the object hits the water, the forces are balanced and the object will stop. Support your answer with reasoning. 21. a) For a constant force, if the duration of impact upon an object is doubled, how is the impulse affected? b). How is the resulting change in momentum affected? 22. If the time of impact in a collision is extended by four times, by how much is the force of impact altered? 23. Why is it important to follow through when trying to hit a home run? 24. For how long a time must a tow truck pull with a force of 550 N on a stalled 1200 kg car to give it a forward velocity of 2.0 m/s? 25. A crane does work of 13,500 J with a force of 5200 N to lift a beam. How far can the beam be lifted (in meters)? 26. A 3 kg ball is rolling 2 m/s. How much kinetic energy does it have? 27. Which one of the following has an appropriate unit? A) work - joule B) power - watt C) force - newton D) All of the above. 28. The potential energy of a ball on the ground is zero. If the ball is then moved to the bottom of a hole, its potential energy is A) negative. B) non existent. C) same as it was on the surface. D) zero. 29. You can find the kinetic energy of a book of a known mass just before it hits the floor after falling a known distance by using which equation? A) K.E. = ½ mv 2 B) W = Fd C) P.E. = mgh D) None of the above. 30. Roughly, what fraction of our nation's current energy needs in total is supplied by coal? A) 80% B) 10% C) 40% D) 20%

5 31. The equilibrium rule F net = 0 applies to A) objects or systems at rest. B) objects or systems in uniform motion in a straight line. C) both D) neither 32. Whirl a rock at the end of a string and it follows a circular path. If the string breaks, the rock tends to A) continue in a circular path. B) fall straight downward. C)spiral inward. D) follow a straight-line path. 33. Newton's second law directly involves A) acceleration. B) velocity. C) speed. D) none of the above 34. A heavy truck and a small truck roll down a hill. Neglecting friction, at the bottom of the hill the heavy truck has greater A) speed. B) momentum. C) acceleration. D) all of the above E) none of the above 35. A 4-kg ball has a momentum of 12 kg m/s. What is the ball's speed? 36. You're driving down the highway and a lovebug spatters onto your windshield. After collision, which has the greater acceleration? Why? 37. Distinguish between inertia, mass, and weight. 38. Why are automobiles that collapse in collisions safer than more rigid cars?