Final Exam MAE 145 Spring 2023

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Final Exam MAE 145 Spring 2023

Quiz Instructions

Reminder: "quadrilateral linkage" is the same as "4R linkage".

Question 1                                           5 pts

What is the mechanical advantage of the wedge shown in the following graph? The angle alpha is equal to 60 degrees.

1.73

1

1.41

0.58

Question 2                                      5 pts

Which linkage system has mobility equal to one?

All of the above

Question 3                                         5 pts

The no-load speed and the stall torque of an electric motor are 2000 rpm and 2700 in lbf, respectively (where there is a linear relationship between the torque and motor speed). What is the motor torque (units of in*lbf) when the motor speed is 1000 rpm?

1350

2200

1150

2700

Question 4                                   5 pts

Transmission shifts the power from the motor to the wheels according to the graph below. What is, for that speed ratio, the most appropriate transmission type?

clutch overdrive

belt or cable drive

gear train

linkage system

Question 5                                5 pts

In the picture below, the small gear on the left is the input and the large gear on the right is the output. All small gears have 8 teeth and all large gears have 15 teeth. If the input gear spins at 1620 rpm CCW, how fast does the output gear spin?

246 rpm CW

212 rpm CW

10676 rpm CW

10677 rpm CW

Question 6                               5 pts

Consider the planetary gear train below with annular gear fixed. The sun and planets both have 12 teeth and the annular gear has 36 teeth. The carrier is rotating at 100 RPM. What is the angular velocity of the sun gear?

400 RPM

300 RPM

25 RPM

33.3 RPM

Question 7                               5 pts

If a car (with all four wheels of the same diameter) is going straight without turning and left rear wheel is rotating at 100 RPM, the carrier of the differential is rotating at:

0 RPM

200 RPM

100 RPM

50 RPM

Question 8                                  5 pts

In the schematics below the fixed carrier train ratio R is equal to 4. For the situation with a fixed sun gear, when the input gear is the ring gear and the output gear is the carrier, what is the gear ratio?

-1.25

0.75

0.85

1.25

Question 9                         5 pts

For a given input angle θ, the velocity loop equations are:

The result of taking the derivative the position loop equation with respect to time.

All of these

Two linear equations in two unknowns that are solved using Cramer's rule

Question 10                         5 pts

A car's suspension can be represented by the inverted slider crank represented in the illustration below. If at the value of theta = 0 degrees, a = 0.4 m and r = 1.2 m we were to replace the actual spring (with stiffness k) by the equivalent spring but placed above the tire (the tire's location is indicated by arrow Fout), the stiffness of that imaginary spring with respect to the original spring's stiffness (k) will be ...

equal to the original value k

9 times smaller

4 times smaller

4 times greater

Question 11                           5 pts

Compute the angle (in degrees), given that a=2, h=6.5, b=4, c =3.5, c =1.2, =49.4 and =90 . Note we consider the origin to be at point O here, so the equations used here match the derivations from the Homework 5 reference file. Answers are rounded to the nearest hundredth.

30.68

35.42

25.72

20.13

Question 12                        5 pts

Which of the following are equivalent?

SELECT ALL THAT APPLY. (Two)

Mechanical advantage

Torque

Speed ratio

Time ratio

Question 13                          5 pts

The instant center for the quadrilateral linkage in this configuration is the point I . Let R1 = 25cm, R2 = 50cm, and Link 3 = 20cm. What is the mechanical advantage MA of the linkage at this instant?

None of these

2

0.5

1

Question 14                      5 pts

Rear-wheel-drive cars typically have ...

parallel steering geometry

negligible bump steer

double-A arm suspension

slight toe-in

Question 15                       5 pts

What is the maximum velocity achieved by a car that starts at rest on a straight track of length 200m? The car's acceleration is not limited by the engine's power as it is quite considerable. The coefficient of friction of the track is μ=0.4. The gravitational acceleration is 9.8 m/s2 .

22.1 m/s

31.3 m/s

52.4 m/s

39.6 m/s