1. Instructor: Dr. Tatiana Erukhimova
Physics 218: Mechanics
Instructor: Dr. Tatiana Erukhimova
Lectures 11, 12

2. H βt Coefficient of friction:  V0=0
Find the equation that could be solved to find the velocity of the block when it reaches the top.

3. A block of mass 20 kg is pushed against a vertical surface as shown
A block of mass 20 kg is pushed against a vertical surface as shown. The coefficient of friction between the surface and the block is 0.2. If θ=300, what is the minimum magnitude of P to hold the block still? P θ

4. A wedge with mass M rests on a frictionless horizontal tabletop
A wedge with mass M rests on a frictionless horizontal tabletop. A block with mass m is placed on the wedge and a horizontal force F is applied to the wedge. What must the magnitude of F be if the block is to remain at a constant height above the tabletop?

5. A Problem With First Year Physics Strings and Pulleys
m1, m2 are given
m2>m1 m2
String is massless and unstretchable
Find accelerations of m1 and m2 (assume no friction in pulley)

6. Block 1, of mass m1, is placed at rest on an inclined plane
Block 1, of mass m1, is placed at rest on an inclined plane. It is attached by a massless, unstretchable string to block 2, of mass m2. The pulley is massless and frictionless and just changes the direction of the tension in the string. The coefficient of friction between the plane and m1 is the constant . 1 2
Determine what range of values for mass m2 will keep the system at rest.
Find acceleration if mass 2 goes down.

7. Friction everywhere. 2 F 1
Find F necessary to drag the box 1 at constant speed.

8. The advantage of a pulley
What minimum force F is needed to lift the piano of mass M?

10. The Elevator Problem

11. Have a great day!
Reading: Chapters 5,6