Chapter_6_09 - Problems from Chapter 6 6.3 A person pushes...

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

View Full Document Right Arrow Icon
Problems from Chapter 6 6.3 A person pushes horizontally with a force of 220 N on a 55 kg crate to move it across a level Foor. The coef±cient of kinetic friction is 0.35. What is the magnitude of (a) the frictional force and (b) the crate’s acceleration. F F f N mg ma y = 0 = N mg N = mg F f = μ N = mg = 0.35 55 kg 9.8 m / s 2 = 188.65 N ma x = F F f a x = F F f m = 220 N 188.65 N 55 kg = 0.57 m / s 2 6.7. A 3.5 kg block is pushed along a horizontal Foor by a force ² of magnitude 15N at an angle of 40 degrees with the horizontal. The coef±cient of kinetic friction between the block and the Foor is 0.25. Calculate the magnitudes of (a) The frictional force on the block from the Foor and (b) the acceleration of the block. N F mg F f N F F f θ We can now write the forces in the vertical and horizontal directions: Vertical 0 = N F sin θ N = + F sin Horizontal ma = F cos F f = F cos N a = F cos ( + F sin ) m
Background image of page 1

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

View Full DocumentRight Arrow Icon
F f = μ ( mg + F sin θ ) = 0.25 (3.5 kg 9.8 m / s 2 + 15 N sin40 ° ) = 10.99 N a = F cos ( mg + F sin ) m = 15 N cos40 ° 10.99 N 3.5 kg = 0.143 m / s 2 6.20 A loaded penguin sled weight 80N rests on a plane inclined at 20 degrees to the horizontal. Between the sled and the plane, the coefFcient of static friction is 0.25, and the coefFcient of kinetic friction is 0.15. (a) What is the minimum magnitude of the force ±, parallel to the plane, that will prevent the sled from slipping down the plane. (b) What is the minimum magnitude ± that will start the sled moving up the plane? (c) What value ± is required to move the sled with constant velocity up the incline. a) We begin by drawing the forces. Since the motion would be downward if ± is too small, we draw ±riction as pointing UP the incline for part a.
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/27/2010 for the course ASD 2456 taught by Professor Jojo during the Spring '10 term at Brooklyn Law School.

Page1 / 9

Chapter_6_09 - Problems from Chapter 6 6.3 A person pushes...

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

View Full Document Right Arrow Icon
Ask a homework question - tutors are online