For Al, its atomic number is 13 and its mass number is 27. How many neutrons does it have?

Slow-moving vehicles are prohibited from traveling on expressways or on roadways with a minimum posted speed limit greater than

Bumek [7]

<span>Slow-moving vehicles are prohibited from traveling on expressways or on roadways with a minimum posted speed limit greater than 40mph, and should use the right lane of travel on divided highways.
As slow moving vehicles should use the right lane, fast moving vehicles should use the left lane.
Before start driving, we should learn all the guidelines and rules for this, to avoid any type of inconvenience.</span>

7 0

3 years ago

A block weighing 400 kg rests on a horizontal surface and supports on top of it ,another block of weight 100 kg which is attache

Paladinen [302]

Answer:

$F_a=1470\ N$

Explanation:

<u>Friction Force</u>

When objects are in contact with other objects or rough surfaces, the friction forces appear when we try to move them with respect to each other. The friction forces always have a direction opposite to the intended motion, i.e. if the object is pushed to the right, the friction force is exerted to the left.

There are two blocks, one of 400 kg on a horizontal surface and other of 100 kg on top of it tied to a vertical wall by a string. If we try to push the first block, it will not move freely, because two friction forces appear: one exerted by the surface and the other exerted by the contact between both blocks. Let's call them Fr1 and Fr2 respectively. The block 2 is attached to the wall by a string, so it won't simply move with the block 1.

Please find the free body diagrams in the figure provided below.

The equilibrium condition for the mass 1 is

$\displaystyle F_a-F_{r1}-F_{r2}=m.a=0$

The mass m1 is being pushed by the force Fa so that slipping with the mass m2 barely occurs, thus the system is not moving, and a=0. Solving for Fa

$\displaystyle F_a=F_{r1}+F_{r2}.....[1]$

The mass 2 is tried to be pushed to the right by the friction force Fr2 between them, but the string keeps it fixed in position with the tension T. The equation in the horizontal axis is

$\displaystyle F_{r2}-T=0$

The friction forces are computed by

$\displaystyle F_{r2}=\mu \ N_2=\mu\ m_2\ g$

$\displaystyle F_{r1}=\mu \ N_1=\mu(m_1+m_2)g$

Recall N1 is the reaction of the surface on mass m1 which holds a total mass of m1+m2.

Replacing in [1]

$\displaystyle F_{a}=\mu \ m_2\ g\ +\mu(m_1+m_2)g$

Simplifying

$\displaystyle F_{a}=\mu \ g(m_1+2\ m_2)$

Plugging in the values

$\displaystyle F_{a}=0.25(9.8)[400+2(100)]$

$\boxed{F_a=1470\ N}$

8 0

3 years ago

You lift a large bag of flour from the floor to a 2.5m high counter, doing 400J of work in 2 seconds. How much force did you app

oksian1 [2.3K]

<h2>The man have to apply force of 160 N</h2>

Explanation:

The work done to lift the bag of weight mg through height 2.5 m is 400 J

The work done can be found by relation W = mg x h

Thus mg = $\frac{W}{h}$ = $\frac{400}{2.5}$ = 160 N

Therefore the man have to apply the force of 160 N

7 0

3 years ago

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A student drops a rock from a bridge to the water 12.7 m below. with what speed does the rock strike the water? the acceleration

kolezko [41]

The rock strike the water with the speed of 15.78 m/sec.

The speed by which rock hit the water is calculated by the formula

v= $\sqrt{2gh}$

v= $\sqrt{2*9.8*12.7}$

v=15.78 m/sec

Hence, the rock strike the water with the speed of 15.78 m/sec.

7 0

3 years ago

The amount of water on earth now is the same as when dinosaurs existed. True or false? PLEASEEEEE HELPPPPPP

Mnenie [13.5K]

Answer: True

Explanation: Because of the way this water cycle has always circulated our planet, there is indeed a chance that the water in your glass is the same water that thirsty dinosaurs were drinking about 65 million years ago

5 0

2 years ago

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