Question 1

You push downward on a trunk at an angle 2  below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is
0)61, what is the most massive trunk you will be able to move?
A) 81 kg
B) 73 kg
C) 112 kg
D) 93 kg

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Question 2

A system consisting of blocks, a light frictionless pulley, a frictionless incline, and very light connecting wires is shown in the figure. The wires pull on the left-hand blocks parallel to the surface of the ramp. The  9.0-kg  block accelerates downward when the system is released gently from rest.
(a) What is the magnitude of the acceleration of the  9.0-kg block?
(b) What is the tension in the wire connecting the two blocks on the incline?

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Question 3

A slanted roof rises at  ° above the horizontal, and the straight-line distance from the top
of the roof to the bottom edge is 4.5 m. The roof is covered with ice, so it offers no friction
to objects sliding on it. A piece of ice at the top suddenly breaks loose and begins to slide
down from rest.
(a) How long will it take for the ice to reach the bottom edge of the roof?
(b) How fast will the ice be traveling just as it reaches the bottom edge?

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Question 4

The figure shows a system consisting of three blocks, a light frictionless pulley, and light
connecting ropes that act horizontally on the upper two blocks. The 9.0-kg block is on a
perfectly smooth horizontal table. The surfaces of the 12-kg block are rough, with µk =
0.30 between the 12-kg and 9.0-kg blocks. The mass M of the hanging block is set so that it
descends at a constant velocity of 3.25 m/s.
(a) What is the mass M of the hanging block?
(b) The mass M is now changed to 5.0 kg, causing it to accelerate downward after it is
released. What is the acceleration of the hanging mass?

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Question 5

A horizontal 52-N force is needed to slide a 50-kg box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor?
A) 0.11
B) 0.10
C) 0.09
D) 0.13

Accepted Answer

The force of kinetic friction is equal to the coefficient of kinetic friction times the normal force. The normal force is equal to the weight of the box, which is 50 kg * 9.8 m/s^2 = 490 N. Therefore, the force of kinetic friction is 52 N = 0.11 * 490 N.

Question 6

A 7.5-kg stone moves up frictionless hill that slopes upward at  above the horizontal. If the stone has an initial velocity of  8.5 m/s at the bottom, how far (as measured along the surface of the hill) will it go before stopping?

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Question 7

You push horizontally on a 120-N box that is initially resting on a horizontal table. The
coefficient of static friction between the box and the table is 0.75, and the coefficient of
kinetic friction is 0.40. Find the friction force on the box if the push is equal to (a) 84 N; (b)
94 N.

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Question 8

In a shuffleboard game, the puck slides a total of 12 m on a horizontal surface before coming to rest. If the coefficient of kinetic friction between the puck and board is 0.10, what was the initial
Speed of the puck?
A) 3.8 m/s
B) 48.5 m/s
C) 4.8 m/s
D) 4.3 m/s

Accepted Answer

The initial speed of the puck can be found using the work-energy principle. The work done by friction is equal to the change in kinetic energy. The work done by friction is $W = f_k \cdot d = \mu_k \cdot m \cdot g \cdot d$, where $f_k$ is the force of kinetic friction, $\mu_k$ is the coefficient of kinetic friction, $m$ is the mass of the puck, $g$ is the acceleration due to gravity (9.8 m/s$^2$), and $d$ is the distance (12 m). The change in kinetic energy is $\Delta KE = \frac{1}{2} m v^2 - 0$, since the puck comes to rest. Setting the work done by friction equal to the change in kinetic energy and solving for $v$ (initial speed), we don't need the mass of the puck as it cancels out. Using the given coefficient of kinetic friction (0.10) and the distance (12 m), we can solve for $v$. The calculation simplifies to $v = \sqrt{2 \cdot \mu_k \cdot g \cdot d}$, which gives $v = \sqrt{2 \cdot 0.10 \cdot 9.8 \cdot 12} \approx 4.8$ m/s.

Question 9

Jason takes off across level water on his jet-powered skis. The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis produce a forward thrust of 200 N and have a
Coefficient of kinetic friction with water of 0.10. Unfortunately, the skis run out of fuel after only 41 S) How far from his starting point has Jason traveled when he finally coasts to a stop?
A) 1400 m
B) 2000 m
C) 3900 m
D) 2900 m

Accepted Answer

The net force while the skis are powered is the thrust minus the friction force. The friction force is calculated as the coefficient of kinetic friction times the normal force (which equals the gravitational force here). Using Newton's second law, we find the acceleration while powered. After the fuel runs out, Jason decelerates due to friction alone. We calculate the distance traveled during both phases (powered and coasting) and sum them to find the total distance.

Question 10

A  150-N crate is being pulled up a perfectly smooth ramp that slopes upward at  by a pull that is directed at  above the surface of the ramp. What is the magnitude of the pull required to make the crate move up the ramp at a constant velocity of  1.75 m/s?

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Question 11

A flatbed truck is carrying a 20.0-kg crate along a level road. The coefficient of static friction between the crate and the bed is 0.400, and the coefficient of kinetic friction is 0.300. What is the
Maximum acceleration that the truck can have if the crate is to stay in place relative to the truck?
A) 7.84 m/s²
B) 8.00 m/s²
C) 78.5 m/s²
D) 3.92 m/s²
E) 196 m/s²

Accepted Answer

The maximum acceleration is determined by the static friction, which is the product of the coefficient of static friction (0.400) and gravitational acceleration (9.8 m/s²). Thus, a_max = 0.400 * 9.8 m/s² = 3.92 m/s².

Question 12

A 5.0-kg box slides on the surface on a ramp that rises at  above the horizontal. The coefficient of kinetic friction between the box and the surface of the ramp is  0.60 . What are the magnitude and direction of the acceleration of the box if it is sliding (a) up the ramp, (b) down the ramp?

Accepted Answer

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Question 13

A driver in a 1000-kg car traveling at 24 m/s slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the level road is 0.80, how long will the skid marks be?
A) 30 m
B) 34 m
C) 46 m
D) 37 m

Accepted Answer

The work-energy principle can be used here. The initial kinetic energy is converted into work done against friction. The frictional force is the product of the normal force (equal to the weight of the car) and the coefficient of friction. Solving for the distance gives approximately 37 m.

Question 14

During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the horizontal ice before it stops due to friction. What is the coefficient of kinetic friction between the puck and
The ice?
A) 0.090
B) 0.11
C) 0.12
D) 0.10

Accepted Answer

To find the coefficient of kinetic friction ($\mu_k$), we can use the work-energy principle. The work done by friction is equal to the change in kinetic energy. The formula for the work done by friction is $W = \mu_k F_n d$, where $F_n$ is the normal force, and $d$ is the distance. Since the puck is on a horizontal surface, $F_n = mg$, where $m$ is the mass of the puck and $g$ is the acceleration due to gravity. The change in kinetic energy ($\Delta KE$) is given by $\frac{1}{2}mv^2 - 0$, since the puck stops ($v = 0$).Setting the work done by friction equal to the change in kinetic energy gives us:$$\mu_k mgd = \frac{1}{2}mv^2$$Solving for $\mu_k$ gives:$$\mu_k = \frac{v^2}{2gd}$$Substituting $v = 10 \, m/s$, $g = 9.8 \, m/s^2$, and $d = 50 \, m$ gives:$$\mu_k = \frac{(10)^2}{2(9.8)(50)} = \frac{100}{980} = 0.102$$Rounded to two decimal places, the coefficient of kinetic friction is 0.10.

Question 15

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A horizontal 140-N force is applied to the box. What is the friction force on the box?
A) 140 N
B) 16.5 N
C) 160 N
D) 42 N
E) 0.00 N

Accepted Answer

The friction force equals the applied force (140 N) because the box does not move, indicating that static friction is at its maximum value but does not exceed the applied force.

Question 16

A 2.8-kg tool can move on a perfectly smooth ramp that slants at  above the horizontal. What are the magnitude and direction of the acceleration of this tool if it is sliding (a) up the ram, (b) down the ramp?

Accepted Answer

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Question 17

A 15-kg block is on a frictionless ramp that is inclined a  ° above the horizontal. It is connected by a very light string over an ideal pulley at the top edge of the ramp to a hanging 19-kg block, as
Shown in the figure. The string pulls on the 15-kg block parallel to the surface of the ramp. Find the
Magnitude of the acceleration of the 19-kg block after the system is gently released?

A) 
B) 
C) 
D)

Accepted Answer

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Question 18

Accepted Answer

The answer of ...

Question 19

Jason takes off across level water on his jet-powered skis. The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). The skis produce a forward thrust of 200 N and have a
Coefficient of kinetic friction with water of 0.10. Unfortunately, the skis run out of fuel after only 90 S) What is Jason's top speed?
A) 90 m/s
B) 24 m/s
C) 150 m/s
D) 240 m/s

Accepted Answer

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Question 20

A flatbed truck is carrying a 20-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is  0.40 , and the coefficient of kinetic friction is  0.30 . What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?
A) 
B) 
C) 
D) 
E)

Accepted Answer

The answer of A flatbed truck is carrying a 20-kg...

Quiz 4: Dynamics: Newtons Laws of Motion

You push downward on a trunk at an angle 2 below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0) 61, what is the most massive trunk you will be able to move?

A horizontal 52-N force is needed to slide a 50-kg box across a flat surface at a constant velocity of 3.5 m/s. What is the coefficient of kinetic friction between the box and the floor?

A 7.5-kg stone moves up frictionless hill that slopes upward at above the horizontal. If the stone has an initial velocity of 8.5 m/s at the bottom, how far (as measured along the surface of the hill) will it go before stopping?

You push horizontally on a 120-N box that is initially resting on a horizontal table. The coefficient of static friction between the box and the table is 0.75, and the coefficient of kinetic friction is 0.40. Find the friction force on the box if the push is equal to (a) 84 N; (b) 94 N.

In a shuffleboard game, the puck slides a total of 12 m on a horizontal surface before coming to rest. If the coefficient of kinetic friction between the puck and board is 0.10, what was the initial Speed of the puck?

A 150-N crate is being pulled up a perfectly smooth ramp that slopes upward at by a pull that is directed at above the surface of the ramp. What is the magnitude of the pull required to make the crate move up the ramp at a constant velocity of 1.75 m/s?

A 5.0-kg box slides on the surface on a ramp that rises at above the horizontal. The coefficient of kinetic friction between the box and the surface of the ramp is 0.60 . What are the magnitude and direction of the acceleration of the box if it is sliding (a) up the ramp, (b) down the ramp?

A driver in a 1000-kg car traveling at 24 m/s slams on the brakes and skids to a stop. If the coefficient of friction between the tires and the level road is 0.80, how long will the skid marks be?

During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the horizontal ice before it stops due to friction. What is the coefficient of kinetic friction between the puck and The ice?

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30. A horizontal 140-N force is applied to the box. What is the friction force on the box?

A 2.8-kg tool can move on a perfectly smooth ramp that slants at above the horizontal. What are the magnitude and direction of the acceleration of this tool if it is sliding (a) up the ram, (b) down the ramp?

A flatbed truck is carrying a 20-kg crate up a sloping road. The coefficient of static friction between the crate and the bed is 0.40 , and the coefficient of kinetic friction is 0.30 . What is the maximum angle of slope that the truck can climb at constant speed if the crate is to stay in place?