{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

PH101 HW Rotational Kinematics 2

# PH101 HW Rotational Kinematics 2 - This print-out should...

This preview shows pages 1–3. Sign up to view the full content.

This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Find the magnitude of the torque produced by a 4.8 N force applied to a door at a per- pendicular distance of 0.21 m from the hinge. Correct answer: 1 . 008 N · m. Explanation: Let : F = 4 . 8 N , d = 0 . 21 m , and θ = 90 . 0 . τ = F d sin θ = (4 . 8 N) (0 . 21 m) sin 90 . 0 = 1 . 008 N · m . 002 10.0 points An Atwood machine is constructed using a disk of mass 2 . 3 kg and radius 23 . 7 cm. 3 . 7 m 23 . 7 cm 2 . 3 kg ω 1 . 78 kg 1 . 12 kg What is the acceleration of the system? The acceleration of gravity is 9 . 8 m / s 2 . Correct answer: 1 . 59704 m / s 2 . Explanation: Let : m = 2 . 3 kg , R = 23 . 7 cm = 0 . 237 m , m 1 = 1 . 12 kg , m 2 = 1 . 78 kg , and h = 3 . 7 m . Consider the free body diagrams 1 . 78 kg 1 . 12 kg T 2 T 1 m 2 g m 1 g a a The net acceleration a = r α is in the di- rection of the heavier mass m 1 . For the mass m 1 , F net = m 1 a = m 1 g - T 1 T 1 = m 1 g - m 1 a and for the mass m 2 , F net = m 2 a = T 2 - m 2 g T 2 = m 2 a + m 2 g . The pulley is a solid disk, so I = 1 2 m r 2 and τ net = τ ccw - τ cw = I α T 1 r - T 2 r = 1 2 m r 2 a r = 1 2 m r a Multiplying by 2 r gives m a = 2 T 1 - 2 T 2 = 2 ( m 1 - m 2 ) g - 2 ( m 1 + m 2 ) a a = 2 ( m 1 - m 2 ) g m + 2 m 1 + 2 m 2 = 2 (1 . 12 kg - 1 . 78 kg) (9 . 8 m / s 2 ) 2 . 3 kg + 2 (1 . 12 kg) + 2 (1 . 78 kg) = 1 . 59704 m / s 2 . 003 10.0 points

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
A 308 kg merry-go-round in the shape of a horizontal disk with a radius of 1 . 3 m is set in motion by wrapping a rope about the rim of the disk and pulling on the rope. How large a torque would have to be ex- erted to bring the merry-go-round from rest to an angular speed of 3 . 4 rad / s in 2 . 2 s?
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 5

PH101 HW Rotational Kinematics 2 - This print-out should...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online