# dry friction

## Problem 544 | Friction on Wedges

**Problem 544**

The block A in Fig. P-544 supports a load W and is to be raised by forcing the wedge B under it. If the angle of friction is 10° at all surfaces in contact, determine the maximum wedge angle α that will give the wedge a mechanical advantage; i.e., make P less than the weight W of the block.

## Problem 543 | Friction on Wedges

**Problem 543**

To adjust the vertical position of a column supporting 200-kN load, two 5° wedges are used as shown in Fig. P-543. Determine the force P necessary to start the wedges is the angle of friction at all contact surfaces is 25°. Neglect friction at the rollers.

## Problem 542 | Friction on Wedges

**Problem 542**

What force P must be applied to the wedges shown in Fig. P-542 to start them under the block? The angle of friction for all contact surfaces is 10°.

## Problem 541 | Friction on Wedges

**Problem 541**

Determine the force P required to start the wedge shown in Fig. P-541. The angle of friction for all surfaces in contact is 15°.

## Problem 540 | Friction on Wedges

**Problem 540**

As shown in Fig. P-540, two blocks each weighing 20 kN and resting on a horizontal surface, are to be pushed apart by a 30° wedge. The angle of friction is 15° for all contact surfaces. What value of P is required to start movement of the blocks? How would this answer be changed if the weight of one of the blocks were increased by 30 kN?

## Problem 539 | Friction on Wedges

**Problem 539**

The block A in Fig. P-539 supports a load W = 100 kN and is to be raised by forcing the wedge B under it. The angle of friction for all surfaces in contact is f = 15°. If the wedge had a weight of 40 kN, what value of P would be required (a) to start the wedge under the block and (b) to pull the wedge out from under the block?

## Problem 538 | Friction on Wedges

**Problem 538**

In Problem 537, determine the value of P acting to the left that is required to pull the wedge out from under the 40-kN block.

## Problem 536 | Friction on Wedges

**Problem 536**

in Fig. P-536, determine the minimum weight of block B that will keep it at rest while a force P starts blocks A up the incline surface of B. The weight of A is 100 lb and the angle of friction for all surfaces in contact is 15°.

## Problem 535 | Friction on Wedges

**Problem 535**

A wedge is used to split logs. If φ is the angle of friction between the wedge and the log, determine the maximum angle a of the wedge so that it will remain embedded in the log.

## Problem 533 | Friction

**Problem 533**

A uniform bar AB, weighing 424 N, is fastened by a frictionless pin to a block weighing 200 N as shown in Fig. P-533. At the vertical wall, μ = 0.268 while under the block, μ = 0.20. Determine the force P needed to start motion to the right.