5. A thin walled hoop with diameter of 2.00 meters is spinning at 20.0 rad/s. The mass is 10.0 kg. Negative work of 300.0 J is done to the hoop for 1.50 seconds. (a) What is the new angular velocity? (b) What is the angular d acceleration during the 1.50 seconds? (c) How many radians does it spin bonga 201b61 m 200.0 during the 1.50 seconds? I = mr Answers (a) 18.4 rad/s (b) -1.07 rad/s (c) 28.7 rad 9.00 N Hint - first use PE1 + KE + W1-2 = PE2 + KE2 to find KE2 and then you can find WB Then for parts (b) and (c) use the equations of circular motion 01.02.1 6. I have a solid 1.50 m diameter disk at rest on a stand (it can spin). I apply a tangent force of 100.0 N to the rim for 5.00 seconds. The mass of the disk is 8.00 kg and the moment of inertia is 2.25 kg m2. (a) What is the angular acceleration during that 5.00 seconds? (b) What is the angular velocity at the end of the 5.00 seconds? (c) How much work was done? (d) How many radians did the disk turn in the 5.00 seconds? Answers (a) 33.3 rad/s (b) 167 rad/s (c) 3.14 x 104 J (d) 419 rad O 4. A bicycle wheel has a diameter of 0.640 m and a mass of 1.80 kg. Assume that the wheel is a hoop with all the mass concentrated on the outside radius. The bicycle is placed on a stationary stand, and a resistive force of 12.0 N is applied tangent to the rim of the tire. What force must be applied by a chain passing over a 0.009 m radius sprocket to give the wheel a clockwise acceleration of 1.50 rad/s? the disk turn in the Answer 457 Newtons Hint - Calculate the wheels moment of inertia using I = mr Then use T = 1 to determine the torque I=1-80 (6-10) = 0184 kgm 2= 0164 2= 6.184 (1.50) + 120 (0.24) 09 120 N F