# Engineering Mechanics Questions Help

I need help with these questions. Thank you!

9. The radius of a wheel is 2.5 ft. At a certain instant t1, the angular velocity of the wheel was 1.2 rad per sec and there was a uniform angular acceleration equal to 0.3 rad per sec per sec. At an instant t2, which was 2 sec later than t1, the magnitude of the tangential component of the linear acceleration of a particle on the circumference of the wheel was A. 0.50 fps per sec. C. 1.00 fps per sec. B. 0.75 fps per sec. D. 1.50 fps per sec.

12. A wheel whose radius is 1.5 ft was rolling without slipping along a horizontal surface. At a certain instant, as indicated in Examination Figure 2, the angular velocity of the wheel was 2.5 rad per sec counterclockwise and the angular acceleration was 3 rad per sec per sec counterclockwise. At the specified instant, the horizontal component of the linear velocity of a particle at the point A at the top of the wheel (vertically above O) was A. 1.40 fps to the right. C. 5.50 fps to the left. B. 3.75 fps to the right. D. 7.50 fps to the left.

13. Assuming a flywheel rotates with a uniform angular velocity equal to 120 rpm, and that it was brought to rest in 16 seconds by reducing the angular velocity at a uniform rate, what was the required acceleration in revolutions per second per second? A. –0.00125 rps per sec C. –0.1250 rps per sec B. –0.0125 rps per sec D. 1.250 rps per sec

18. A wheel whose radius is 1.5 was rolling without slipping along a horizontal surface. At a certain instant, (see Examination Figure 2), the angular velocity of the wheel was 2.5 rad per sec. counterclockwise and the angular acceleration was 3 rad per sec per sec clockwise. At the instant specified the magnitude of the vertical component of the linear acceleration of the particle at the point B was A. 4.50 fps per sec. C. 7.50 fps per sec. B. 5.50 fps per sec. D. 9.0 fps per sec.