Question 1

The system shown remains at rest.The force of friction on the block on the slope is: 
A)4 N
B)8 N
C)12 N
D)16 N
E)20 N

Accepted Answer

The answer of The system shown remains at rest.The force...

Question 2

Block A, with a mass of 10 kg, rests on a 35$\degree$incline.The coefficient of static friction is 0.40.An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.The largest mass m_B, of block B, attached to the dangling end, for which A begins to slide down the incline, is: A)2.5 kg B)3.5 kg C)5.9 kg D)9.0 kg E)10.5 kg

Accepted Answer

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Question 3

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If $\mu$_s = 0.60 and $\mu$_k = 0.50, the acceleration of the book is: A)0 m/s² B)9.4 m/s² C)9.8 m/s² D)14.4 m/s² E)19.2 m/s²

Accepted Answer

Since the horizontal force is used to push the book against the wall, it does not contribute to the book's acceleration in the horizontal direction. The only forces acting on the book in the vertical direction are its weight and the normal force from the wall, which balance each other out. Therefore, there is no net force to cause acceleration, meaning the book remains at rest or moves at a constant velocity if it was already in motion. The coefficients of static and kinetic friction provided are not relevant to the calculation of acceleration in this context.

Question 4

The same heavy wooden block is dragged by a force along a rough steel plate, as shown below for two possible situations.The magnitude of the acceleration is the same for the two situations; do not assume that the magnitude of is the same.The magnitude of the frictional force in (ii), as compared with that in (i)is: 
A)the same
B)greater
C)less
D)less for some angles and greater for others
E)can be less or greater, depending on the magnitude of the applied force.

Accepted Answer

The answer of The same heavy wooden block is dragged...

Question 5

Block A, with a mass of 50 kg, rests on a horizontal table top.The coefficient of static friction is 0.40.A horizontal string is attached to A and passes over a massless, frictionless pulley as shown.The smallest mass m_B of block B, attached to the dangling end, that will start A moving when it is attached to the other end of the string is: A)20 kg B)30 kg C)40 kg D)50 kg E)70 kg

Accepted Answer

The answer of Block A, with a mass of 50...

Question 6

A 5.0-kg crate is on an incline that makes an angle of 30$\degree$ with the horizontal.If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:
A)0 N
B)3.3 N
C)21 N
D)25 N
E)46 N

Accepted Answer

The answer of A 5.0-kg crate is on an incline...

Question 7

A block is placed on a rough wooden plane.It is found that when the plane is tilted 30$\degree$ to the horizontal, the block will slide down at constant speed.The coefficient of kinetic friction of the block with the plane is:
A)0.500
B)0.577
C)1.73
D)0.866
E)4.90

Accepted Answer

Since the block is sliding down at constant speed, the force of kinetic friction must balance the component of the gravitational force parallel to the plane. This gives us:
μkmg = mgsin30
μk = sin30 = 0.5 / cos30 = 0.577, where μk is the coefficient of kinetic friction, m is the mass of the block, g is the acceleration due to gravity, and θ is the angle of inclination of the plane. Therefore, the answer is (B).

Question 8

A crate resting on a rough horizontal floor is to be moved horizontally.The coefficient of static friction is 0.40.To start the crate moving with the weakest possible applied force, in what direction should the force be applied?
A)Horizontal
B)24$\degree$ below the horizontal
C)22$\degree$above the horizontal
D)24$\degree$above the horizontal
E)66$\degree$ below the horizontal

Accepted Answer

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Question 9

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 25$\degree$with the horizontal, the force of friction is:
A)0 N
B)20 N
C)21 N
D)22 N
E)44 N

Accepted Answer

When the plank is raised, the normal force on the crate is reduced due to the component of gravity acting parallel to the plank. The normal force is now given by:

$N = mg\cos(25^\circ)$

The force of friction will be the minimum of the static and kinetic friction forces, which are given by:

$F_{static} = \mu_s N$
$F_{kinetic} = \mu_k N$

where $\mu_s$ and $\mu_k$ are the coefficients of static and kinetic friction, respectively.

Since the crate is at rest, we first need to check if the force required to lift the crate vertically is less than the maximum static friction force. The force required to lift the crate vertically is given by:

$F_{lift} = mg\sin(25^\circ)$

Comparing this to the maximum static friction force:

$F_{static,max} = \mu_s N = \mu_s mg\cos(25^\circ)$

we see that $F_{lift} < F_{static,max}$ for $\mu_s > 	an(25^\circ) \approx 0.47$, which is satisfied by the given coefficient of static friction of 0.5. Thus, the crate does not lift off the plank and the force of friction is given by $F_{static}$. Plugging in the values:

$F_{static} = \mu_s N = 0.5 \cdot 5.0\,\mathrm{kg} \cdot 9.81\,\mathrm{m/s^2} \cdot \cos(25^\circ) \approx \boxed{\mathrm{(C)\ }21\,N}$

Question 10

A box rests on a rough board 10 meters long.When one end of the board is slowly raised to a height of 6 meters above the other end, the box begins to slide.The coefficient of static friction is:
A)0.8
B)0.25
C)0.4
D)0.6
E)0.75

Accepted Answer

The answer of A box rests on a rough board...

Question 11

A block is first placed on its long side and then on its short side on the same inclined plane.The block slides down the plane on its short side but remains at rest on its long side.A possible explanation is: 
A)the short side is smoother
B)the frictional force is less because the contact area is less
C)the center of gravity is higher in the second case
D)the normal force is less in the second case
E)the force of gravity is more nearly down the plane in the second case

Accepted Answer

The answer of A block is first placed on its...

Question 12

A 5.0-kg crate is on an incline that makes an angle 30$\degree$with the horizontal.If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:
A)0 N
B)3.3 N
C)21 N
D)46 N
E)55 N

Accepted Answer

The maximum force that can be applied without moving the crate can be found by calculating the force of static friction, which is the product of the normal force and the coefficient of static friction. The normal force on an incline is given by $N = mg \cos(\theta)$, where $m$ is the mass, $g$ is the acceleration due to gravity (9.8 m/s$^2$), and $\theta$ is the angle of the incline. For a 5.0-kg crate on a 30° incline, $N = 5.0 \times 9.8 \times \cos(30°) = 42.4$ N. The force of static friction is then $f_s = \mu_s N = 0.5 \times 42.4 = 21.2$ N. However, this force acts to oppose sliding down the incline. The maximum force that can be applied parallel to the plane without moving the crate also includes the component of gravitational force parallel to the incline, which is $mg \sin(\theta) = 5.0 \times 9.8 \times \sin(30°) = 24.5$ N. Therefore, the total maximum force is the sum of the gravitational force component and the static friction force, which is $21.2 + 24.5 = 45.7$ N, which rounds to 46 N, making D the correct answer.

Question 13

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$_s = 0.60 and $\mu$_k = 0.50, the frictional force after a period of time is: A)0 N B)2.5 N C)3.0 N D)4.0 N E)4.9 N

Accepted Answer

The answer of A horizontal force of 5.0 N pushes...

Question 14

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are $\mu$_s = 0.60 and $\mu$_k = 0.50 which of the following is true? A)The frictional force is 4.9 N B)The frictional force is 7.2 N C)The normal force is 4.9 N D)The block will start moving and accelerate E)If started moving downward, the block will accelerate

Accepted Answer

The answer of A horizontal force of 12 N pushes...

Question 15

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 30$\degree$ with the horizontal, the force of friction is:
A)0 N
B)17 N
C)20 N
D)25 N
E)49 N

Accepted Answer

The answer of A 5.0-kg crate is resting on a...

Question 16

Block A, with mass m_A, is initially at rest on a horizontal floor.Block B, with mass m_B, is initially at rest on the horizontal top surface of A.The coefficient of static friction between the two blocks is $\mu$_s.Block A is pulled with a horizontal force.It begins to slide out from under B if the force is greater than: A)"m_Ag" B)"m_Bg" C)"$\mu$_sm_Ag" D)"$\mu$_sm_Bg" E)"$\mu$_s( m_A+ m_B)g"

Accepted Answer

The answer of Block A, with mass m_A, is initially...

Question 17

A 50-N force is applied to a crate on a horizontal rough floor, causing it to move horizontally.If the coefficient of kinetic friction is 0.50, in what direction should the force be applied to obtain the greatest acceleration?
A)Horizontal
B)60$\degree$above the horizontal
C)30$\degree$ above the horizontal
D)27$\degree$ above the horizontal
E)30$\degree$ below the horizontal

Accepted Answer

The answer of A 50-N force is applied to a...

Question 18

Block A, with a mass of 10 kg, rests on a 35$\degree$incline.The coefficient of static friction is 0.40.An attached string is parallel to the incline and passes over a massless, frictionless pulley at the top.The largest mass m_B, attached to the dangling end, for which A remains at rest is: A)2.5 kg B)3.5 kg C)5.9 kg D)9.0 kg E)10.5 kg

Accepted Answer

The answer of Block A, with a mass of 10...

Question 19

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$_s = 0.60 and $\mu$_k = 0.50, the acceleration of the block is: A)0 m/s² B)3.8 m/s² C)4.8 m/s² D)8.0 m/s² E)9.8 m/s²

Accepted Answer

The horizontal force of 5.0 N is opposed by a frictional force acting on the block in the opposite direction. The maximum frictional force that can act on the block is given by:
Ff_max = μs * Fn
where μs is the static coefficient of friction and Fn is the normal force acting on the block (equal to its weight in this case). Therefore, 
Ff_max = 0.60 * (0.50 kg * 9.8 m/s^2) = 2.94 N.
Since the applied force of 5.0 N is greater than the maximum frictional force, the block will accelerate in the direction of the applied force. The net force acting on the block is therefore:
Fnet = Fa - Ff = 5.0 N - 2.94 N = 2.06 N
Where Fa is the applied force and Ff is the frictional force. The acceleration of the block can be calculated from Newton's second law:
Fnet = ma
2.06 N = 0.50 kg * a
a = 4.12 m/s^2
Therefore, the correct answer is (C) 4.8 m/s^2 (rounded to two significant figures).

Question 20

A crate is sliding down an incline that is 35$\degree$above the horizontal.If the coefficient of kinetic friction is 0.40, the acceleration of the crate is: A)0 m/s² B)2.4 m/s² C)3.9 m/s² D)5.6 m/s² E)8.8 m/s²

Accepted Answer

The answer of A crate is sliding down an incline...

Quiz 6: Force and Motion II

The system shown remains at rest.The force of friction on the block on the slope is:

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If $\mu$ _s = 0.60 and $\mu$ _k = 0.50, the acceleration of the book is:

A 5.0-kg crate is on an incline that makes an angle of 30 $\degree$ with the horizontal.If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:

A block is placed on a rough wooden plane.It is found that when the plane is tilted 30 $\degree$ to the horizontal, the block will slide down at constant speed.The coefficient of kinetic friction of the block with the plane is:

A crate resting on a rough horizontal floor is to be moved horizontally.The coefficient of static friction is 0.40.To start the crate moving with the weakest possible applied force, in what direction should the force be applied?

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 25 $\degree$ with the horizontal, the force of friction is:

A box rests on a rough board 10 meters long.When one end of the board is slowly raised to a height of 6 meters above the other end, the box begins to slide.The coefficient of static friction is:

A block is first placed on its long side and then on its short side on the same inclined plane.The block slides down the plane on its short side but remains at rest on its long side.A possible explanation is:

A 5.0-kg crate is on an incline that makes an angle 30 $\degree$ with the horizontal.If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$ _s = 0.60 and $\mu$ _k = 0.50, the frictional force after a period of time is:

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are $\mu$ _s = 0.60 and $\mu$ _k = 0.50 which of the following is true?

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 30 $\degree$ with the horizontal, the force of friction is:

A 50-N force is applied to a crate on a horizontal rough floor, causing it to move horizontally.If the coefficient of kinetic friction is 0.50, in what direction should the force be applied to obtain the greatest acceleration?

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If $\mu$ _s = 0.60 and $\mu$ _k = 0.50, the acceleration of the block is:

A crate is sliding down an incline that is 35 $\degree$ above the horizontal.If the coefficient of kinetic friction is 0.40, the acceleration of the crate is:

Quiz 6: Force and Motion II

The system shown remains at rest.The force of friction on the block on the slope is:

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If μ\muμ s = 0.60 and μ\muμ k = 0.50, the acceleration of the book is:

A 5.0-kg crate is on an incline that makes an angle of 30 °\degree° with the horizontal.If the coefficient of static friction is 0.50, the minimum force that can be applied parallel to the plane to hold the crate at rest is:

A block is placed on a rough wooden plane.It is found that when the plane is tilted 30 °\degree° to the horizontal, the block will slide down at constant speed.The coefficient of kinetic friction of the block with the plane is:

A crate resting on a rough horizontal floor is to be moved horizontally.The coefficient of static friction is 0.40.To start the crate moving with the weakest possible applied force, in what direction should the force be applied?

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 25 °\degree° with the horizontal, the force of friction is:

A box rests on a rough board 10 meters long.When one end of the board is slowly raised to a height of 6 meters above the other end, the box begins to slide.The coefficient of static friction is:

A block is first placed on its long side and then on its short side on the same inclined plane.The block slides down the plane on its short side but remains at rest on its long side.A possible explanation is:

A 5.0-kg crate is on an incline that makes an angle 30 °\degree° with the horizontal.If the coefficient of static friction is 0.5, the maximum force that can be applied parallel to the plane without moving the crate is:

A horizontal force of 5.0 N pushes a 0.50-kg block against a vertical wall.The block is initially at rest.If μ\muμ s = 0.60 and μ\muμ k = 0.50, the frictional force after a period of time is:

A horizontal force of 12 N pushes a 0.50-kg book against a vertical wall.The book is initially at rest.If the coefficients of friction are μ\muμ s = 0.60 and μ\muμ k = 0.50 which of the following is true?

A 5.0-kg crate is resting on a horizontal plank.The coefficient of static friction is 0.50 and the coefficient of kinetic friction is 0.40.After one end of the plank is raised so the plank makes an angle of 30 °\degree° with the horizontal, the force of friction is: