Ask question

Ask question

All categories

3 years ago

11

6. Jim wishes to push a 100. N wood crate across a wood floor.What is the minimum horizontal force that would be required to sta

rt the crate moving?

2 answers:

sergejj [24]3 years ago

7 0

I want to say the answer is 42N

Usimov [2.4K]3 years ago

5 0

Answer:

50 N

Explanation:

The minimum horizontal force required to start the crate moving must be equal to the maximum force of static friction that acts between the floor and the crate.

The maximum force of static friction is given by:

$F_f = \mu N$

where

$\mu$ is the coefficient of static friction

$N$ is the normal reaction exerted by the floor on the crate.

For wood-wood, as in this case, the maximum coefficient of static friction is about $\mu=0.5$ .

For a horizontal surface, the normal reaction is equal to the weight of the object, so in this case $N=100 N$ . Therefore, the minimum horizontal force required will be:

$F=F_f = \mu N=(0.5)(100 N)=50 N$

You might be interested in

What is the force per unit area at this point acting normal to the surface with unit nor- Side View √√ mal vector n = (1/ 2)ex +

Mumz [18]

Complete Question:

Given $\sigma = \left[\begin{array}{ccc}10&12&13\\12&11&15\\13&15&20\end{array}\right]$ at a point. What is the force per unit area at this point acting normal to the surface with $\b n = (1/ \sqrt{2} ) \b e_x + (1/ \sqrt{2}) \b e_z$ ? Are there any shear stresses acting on this surface?

Answer:

Force per unit area, $\sigma_n = 28 MPa$

There are shear stresses acting on the surface since $\tau \neq 0$

Explanation:

$\sigma = \left[\begin{array}{ccc}10&12&13\\12&11&15\\13&15&20\end{array}\right]$

equation of the normal, $\b n = (1/ \sqrt{2} ) \b e_x + (1/ \sqrt{2}) \b e_z$

$\b n = \left[\begin{array}{ccc}\frac{1}{\sqrt{2} }\\0\\\frac{1}{\sqrt{2} }\end{array}\right]$

Traction vector on n, $T_n = \sigma \b n$

$T_n = \left[\begin{array}{ccc}10&12&13\\12&11&15\\13&15&20\end{array}\right] \left[\begin{array}{ccc}\frac{1}{\sqrt{2} }\\0\\\frac{1}{\sqrt{2} }\end{array}\right]$

$T_n = \left[\begin{array}{ccc}\frac{23}{\sqrt{2} }\\0\\\frac{27}{\sqrt{33} }\end{array}\right]$

$T_n = \frac{23}{\sqrt{2} } \b e_x + \frac{27}{\sqrt{2} } \b e_y + \frac{33}{\sqrt{2} } \b e_z$

To get the Force per unit area acting normal to the surface, find the dot product of the traction vector and the normal.

$\sigma_n = T_n . \b n$

$\sigma \b n = (\frac{23}{\sqrt{2} } \b e_x + \frac{27}{\sqrt{2} } \b e_y + \frac{33}{\sqrt{2} } \b e_z) . ((1/ \sqrt{2} ) \b e_x + 0 \b e_y +(1/ \sqrt{2}) \b e_z)\\\\\sigma \b n = 28 MPa$

If the shear stress, $\tau$ , is calculated and it is not equal to zero, this means there are shear stresses.

$\tau = T_n - \sigma_n \b n$

$\tau = [\frac{23}{\sqrt{2} } \b e_x + \frac{27}{\sqrt{2} } \b e_y + \frac{33}{\sqrt{2} } \b e_z] - 28( (1/ \sqrt{2} ) \b e_x + (1/ \sqrt{2}) \b e_z)\\\\\tau = [\frac{23}{\sqrt{2} } \b e_x + \frac{27}{\sqrt{2} } \b e_y + \frac{33}{\sqrt{2} } \b e_z] - [ (28/ \sqrt{2} ) \b e_x + (28/ \sqrt{2}) \b e_z]\\\\\tau = \frac{-5}{\sqrt{2} } \b e_x + \frac{27}{\sqrt{2} } \b e_y + \frac{5}{\sqrt{2} } \b e_z$

$\tau = \sqrt{(-5/\sqrt{2})^2 + (27/\sqrt{2})^2 + (5/\sqrt{2})^2} \\\\ \tau = 19.74 MPa$

Since $\tau \neq 0$ , there are shear stresses acting on the surface.

3 0

2 years ago

A car speeds up from 13 m/s to 23 m/s in 30 seconds. What is the

Lapatulllka [165]

acceleration of the car = 0.33 m/s²

Explanation:

To calculate the acceleration of the car we use the following formula:

acceleration = change in velocity / time

change in velocity = final velocity - initial velocity

change in velocity = 23 m/s - 13 m/s = 10 m/s

change in velocity = 10 m/s

acceleration = 10 m/s / 30 s

acceleration = 0.33 m/s²

Learn more about:

acceleration

brainly.com/question/4134594

brainly.com/question/1213762

#learnwithBrainly

8 0

3 years ago

What are noble gases?

Bas_tet [7]

Answer:

noble gases are basically a group of gases that are similar in their chemical compounds, theres six of them : helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn).

~batmans wife dun dun dun.....

6 0

3 years ago

What is a list of solid mixtures in a classroom?

OLEGan [10]

Well,
1.} book
2.} computer
3.} desk
4.} chair
5.} pencil
6.} eraser
7.} dry erase board
8.} ruler
9.} calculator
10.} TV
and etc

6 0

3 years ago

What does the statement "all motion is relative"<br> mean?

tekilochka [14]

The statement that motion is relative is an important concept in physics. The meaning behind this statement is that the motion of an object is relative to either the frame of reference of the observer, or to another distinct frame of reference.

4 0

3 years ago