# MCQs on mechanics, fluid mechanics, heat & thermodynamics

1) A person paddling a canoe travels five miles down a canal and then seven miles up the canal.

a) How far did the person travel?

b) What is his final displacement?

2) A test vehicle on a track goes through photo gates spaced 25 m apart at the following times: 2.00sec, 3.30sec, 4.30sec

a) Plot the position versus time of the vehicle.

b) Plot the average speed of the vehicle in the time intervals versus time.

3) A rally driver has to maintain a constant speed between checkpoints. She arrives at these points at the following times

26 mi at 31 min 12 sec

48 mi at 57 min 24 sec

87 mi at 1 hr 43 min 15 sec

105 mi at 2 hr 8 min and 49 sec

a) What is the most probable (i.e. average) speed that she is trying to maintain?

b) What is her largest deviation from this average speed?

4) What is the acceleration of a vehicle that charges its velocity from 100 km/h to a dead stop in 10 s?

5) You are driving north on a highway. Then, without changing speed, you round a curve and drive east.

a) Does your velocity change?

b) Do you accelerate? Explain

6) In terms of Newton's first law (the law of inertia), how does a car headrest help to guard against whiplash in a rear-end collision?

7) Consider a pair of forces, one having a magnitude of 20 N, and the other having a magnitude of 12 N. What maximum net force is possible for these two forces? What is the minimum net force possible?

8) Start a ball rolling down a bowling alley and you'll find it moves slightly slower with time. Does this violate Newton's law of inertia? Defend your answer.

9) What is the acceleration of a 40-kg block of cement when pulled sideways with a net force of 200N?

10) Two boxes are seen to accelerate at the same rate when a force F is applied to the first box and 4F is applied to the second box. What is the mass ratio of the boxes?

11) If a Mack truck and a Honda Civic have a head-on collision, upon which vehicle is the impact force greater? Which vehicle experiences the greater acceleration? Explain your answers.

12) An iron ball having a mass of 5 kg is lifted from the floor to a height of 2.5 meters above the floor.

a) How much work was done to lift the ball?

b) How much potential energy did the ball gain?

13) If a 600 kg car is moving with a speed of 25 m/s, than what is its kinetic energy? Put your answer in Joules.

14) A 200 g ball is thrown upwards with an initial kinetic energy of 10 Joules. What maximum height will the ball attain? (neglect air resistance)

15) If a 200 g ball is dropped from 100 meters what is its velocity just before it hits the ground? What is its velocity after it has fallen halfway to the ground (50 m)? (neglect air resistance)

16) A pipeline has an entrance diameter of of 2 ft. and an exit diameter of 1 ft. Water flows into the entrance of the pipe at 100 ft/sec. The pressure at the entrance is 200 lb/ft2. Find the velocity and pressure at the exit. (Assume that there is no friction.) (Note: In answering the problems, assume that the density of water is about 62 lb/ft3.)

17) A buoyant object is submerged in water. The buoyant force is measured at 5 lb-ft/sec2. When weighed in the open air, the ball weighs 3 lb. (Remember that open air weight is equal to mass times gravity.) What is the density of the ball? (Note: In answering the problems, assume that the density of water is about 62 lb/ft3.)

18) You want to compute the values of the water pressure at various depths below the surface of a lake. Compute the water pressure at 50 feet below the surface, 100 feet below the surface, and so on down to 500 feet below the surface. Show the results of your calculations in a table. (Note: In answering the problems, assume that the density of water is about 62 lb/ft3.)

19)Answer the following four related questions:

How is the speed that an airfoil (i.e. a wing) is traveling over the top and bottom surfaces related to the pressure that is exerted on the top and bottom surfaces of the wing?

How is the total pressure resolved into lift and drag.

How does drag affect the velocity of the wing?

How is the height that the airfoil will rise to affected by the weight of the airfoil?

20) You have a 16 oz cup of coffee at 180 degrees F. That is way too hot to drink. So you want to cool the coffee off and decide to add some cold water. You add 2 ounces of cold water at 40 degrees F. How much will the water you added heat up? How much will the coffee that you poured the water into cool down?

21)An air bubble at the bottom of a lake has a volume of 15 cm^3. The lake is 40 m deep and has a temperature of 4ºC at the bottom. The bubble then rises to the surface where the temperature is 23 ºC. What is the volume of the bubble just before it reaches the surface?

22)You are sitting behind a curtain watching meters that measure pressure, volume, and temperature of some kind of heat engine. Pressure, volume, and temperature have reached an equilibrium state. Then someone behind the curtain tells you that they are going to add energy to the system. The energy is added and the equilibrium changes. Can you tell whether they did work on the system, heated the system, or a combination of both? Explain your answer.

23)In a refrigerator, heat is transferred from a colder area (the inside of the refrigerator) to a warmer area (the air outside of the refrigerator). Given what you know about internal energy, explain how this is possible.

#### Solution Summary

The problems in this set of multiple choice questions on mechanics, fluid mechanics, heat & thermodynamics have been solved explaining the fundamental principles involved.