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cestrela7 [59]
3 years ago
8

Block A, with mass mA, is initially at rest on a horizontal floor. Block B, with mass mB, is initially at rest on the horizontal

top surface of A. The coefficient of static friction between the two blocks is μs. Block A is pulled with a horizontal force. It begins to slide out from under B if the force is greater than:
(A) mA*g
(B) mB*g
(C) μs*mA*g
(D) μs*mB*g
(E) μs(mA +mB)g
Physics
1 answer:
nexus9112 [7]3 years ago
8 0

Answer:

(E) μs(mA +mB)g

Explanation:

We can apply for mB:

∑ Fx = mB*a   (→)

⇒  Ffriction = mB*a   ⇒  a = Ffriction / mB = μs*N / mB

⇒ a = μs*(mB*g) / mB  ⇒   a = μs*g    (acceleration of the system)

Now, for mA we have

∑ Fx = mA*a   (→)

F - Ffriction = mA*a      ⇒  F = mA*a + Ffriction  

⇒     F = mA*(μs*g) + μs*(mB*g)   ⇒   F = μs*g*(mA + mB)

We must know that the friction acts only between the two blocks

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When a wire with a current is placed in a magnetic field,
Jet001 [13]
A. electrical energy is transformed into mechanical energy.
6 0
3 years ago
The normal force acting on an object and the force of static friction do zero work on the object. However the reason that the wo
spin [16.1K]

Answer:

<em>The normal force is perpendicular to the displacement</em>

<em>The static friction force produces no displacement</em>

Explanation:

Work Done By Special Forces

The work is a physical magnitude that measures the dot product of the force applied to an object by the displacement it produces in it.

W=\vec F\ \vec r

It can be written in its scalar version as

W=F.d.cos\theta

Being F and d the magnitudes of the force and displacement, and \theta the angle between them

If the angle is zero, the work is at maximum, it the angle is 90°, the work is zero. If the angle is between 90° and 180°, the work is negative.

The normal force acts in the vertical direction when the object is being pushed horizontally. It means the angle between the force and the displacement is 90°, thus the work is

W=N.d.cos90^o=0

The work is zero because the force and the displacement are perpendicular

The static friction force exists only when the object is being applied a force of a magnitude not large enough to produce movement, i.e. the object is at rest. If the object is moved, the friction force is still present, but it's called dynamic friction force, usually smaller than the static.

Since in this case, there is no displacement, d=0, and the work is

W=F_r(0)cos180^o=0

3 0
3 years ago
A family car has a mass of 1400 kg. In an accident it hits a wall and goes from a speed of 27 m/s to a standstill in 1.5 seconds
horrorfan [7]

Answer:

The force has been reduced by 8018 N

Explanation:

The impulse exerted on the car during the crash is equal to the product of the force exerted and the duration of the collision, and it is also equal to the change in momentum of the car. So we can write:

F\Delta t = m\Delta v

where:

F is the force exerted on the car

\Delta t is the duration of the collision

m = 1400 kg is the mass of the car

\Delta  v=-27 m/s is the change in velocity of the car

We can re-write the equation as

F=\frac{m\Delta v}{\Delta t}

In the 1st collision, the time is 1.5 seconds, so the force is

F_1=\frac{(1400)(-27)}{1.5}=-25,200 N

In the 2nd collision, the time is increased to 2.2 seconds, so the force is

F_2=\frac{(1400)(-27)}{2.2}=-17,182 N

Therefore, the force has been reduced by:

F_2-F_1=-17,182-(-25,200)=8018 N

4 0
3 years ago
Read 2 more answers
3. Which one of these has the most inertia?
Arte-miy333 [17]

b. A Boeing 747 airplane

Explanation:

The Boeing 747 airplane will have the most inertia of all. Inertia is the tendency of an object to remain at rest or uniform motion.

  • Newton's first law of motion is also regarded as the law of inertia.
  • It states that "an object will remain at rest or uniform motion motion unless acted upon by an external force".
  • A body that has a large mass will be more resistant to any external force that acts on it.
  • The Boeing 747 has the most mass of all and will have the most inertia.

Learn more:

Inertia brainly.com/question/691705

#learnwithBrainly

3 0
3 years ago
In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. at the 10 m position, halfway up,
Mazyrski [523]

On the ball, there is mg of net force.

<h3>How would one describe air resistance?</h3>
  • Air exerts a force known as air resistance. The force works in the opposite direction of an object traveling through the air.
  • While a sports vehicle with a streamlined design will encounter reduced air resistance and experience less drag, the automobile will be able to move more quickly than a truck with a flat front.
<h3>What Causes Air Resistance?</h3>
  • Air resistance, also referred to as "drag," is a force brought on by air. When air specks collide with an object's front, it slows down.
  • The more air particles that impact the object and the larger its surface area, the more resistance it faces.

learn more about air resistance here

brainly.com/question/1385438

#SPJ4

5 0
1 year ago
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