# I need help with a physics problem

**Question description**

1.) Big Ben, the nickname for the clock in Elizabeth Tower (named after the Queen in 2012) in London, has an hour hand 2.70 m long with a mass of 60.0 kg and a minute hand 4.50 m long with a mass of 100 kg (figure). Calculate the total rotational kinetic energy of the two hands about the axis of rotation. (You may model the hands as long, thin rods rotated about one end. Assume the hour and minute hands are rotating at a constant rate of one revolution per 12 hours and 60 minutes, respectively.) answer in J

2.) In the figure below, the hanging object has a mass of *m*_{1} = 0.390 kg; the sliding block has a mass of *m*_{2} = 0.890 kg; and the pulley is a hollow cylinder with a mass of *M* = 0.350 kg, an inner radius of *R*_{1} = 0.020 0 m, and an outer radius of *R*_{2} = 0.030 0 m.Assume the mass of the spokes is negligible. The coefficient of kinetic friction between the block and the horizontal surface is μ_{k} = 0.250. The pulley turns without friction on its axle. The light cord does not stretch and does not slip on the pulley. The block has a velocity of *v*_{i} = 0.820 m/s toward the pulley when it passes a reference point on the table.

(a) Use energy methods to predict its speed after it has moved to a second point, 0.700 m away. answer in m/s

(b) Find the angular speed of the pulley at the same moment. answer in rad/s

3.) A marble and a cube are placed at the top of a ramp. Starting from rest at the same height, the marble rolls without slipping and the cube slides (no kinetic friction) down the ramp. Determine the ratio of the center-of-mass speed of the cube to the center-of-mass speed of the marble at the bottom of the ramp.

v_{cube} |

v_{marble} |

## Tutor Answer

## 8 Reviews

**Quality**

**Communication**

**On Time**

**Value**

Brown University

1271 Tutors

California Institute of Technology

2131 Tutors

Carnegie Mellon University

982 Tutors

Columbia University

1256 Tutors

Dartmouth University

2113 Tutors

Emory University

2279 Tutors

Harvard University

599 Tutors

Massachusetts Institute of Technology

2319 Tutors

New York University

1645 Tutors

Notre Dam University

1911 Tutors

Oklahoma University

2122 Tutors

Pennsylvania State University

932 Tutors

Princeton University

1211 Tutors

Stanford University

983 Tutors

University of California

1282 Tutors

Oxford University

123 Tutors

Yale University

2325 Tutors