next up previous
Next: About this document

Physics 170. Midterm I

Please write your name at the top of the page

There are 4 problems. Each is assigned 25 points.

Problem 1: 25 points

The speed of waves in the deep waters of the Pacific Ocean depends on the acceleration of gravity g, and on the wavelength of the waves (denoted tex2html_wrap_inline23 ), which is measured in meters.

Use dimensional analysis to find the dependence of the speed on g and tex2html_wrap_inline23 .

Problem 2: 25 points

While standing on the edge of a 120 m high cliff, you throw a rock horizontally at 14 m/s.

How far from the bottom of the cliff does it land (i.e. in the horizontal direction) ? Neglect air resistance.

Problem 3: 25 points

A roofer secures a 28-kg toolbox while working on a frictionless metal roof pitched at an angle of 40 tex2html_wrap_inline27 . To do so, he uses a rope running horizontally as shown below.

a) Draw a diagram and show the forces which act on the toolbox.

b) What is the tension in the rope ?

Problem 4: 25 points

A 2.5 kg block is placed on a horizontal board, and the board is gradually tilted upwards (i.e. this is an inclined plane with an adjustable angle of inclination tex2html_wrap_inline29 ). The block remains at rest until the board makes an angle of tex2html_wrap_inline31 38 tex2html_wrap_inline27 to the horizontal at which point it begins to slide.

a) Draw a diagram which show the forces acting on the block.

b) What is the coefficient of static friction between the board and the surface of the 2.5 kg block ?

Tom Browder
Wed Sep 3 13:59:28 HST 1997