Question 1

A locomotive is pulling three train cars along a level track with a force of  100,000 N. The car next to the locomotive has a mass of  80,000 kg, the next one,  50,000 kg, and the last one,  70,000 kg. You can neglect the friction on the cars being pulled.
(a) What is the magnitude of the force between that the  80,000-kg car exerts on the  50,000-kg car?
(b) What is the magnitude of the force that the  50,000-kg car exerts on the  70,000-kg car?

Accepted Answer

The answer of A locomotive is pulling three train cars...

Question 2

The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes 0.53 s for it to reach the floor. What is the mass m of the block on the left? There is no friction or mass in
The pulley, and the connecting rope is very light.

Accepted Answer

The answer of The figure shows a 100-kg block being...

Question 3

A locomotive is pulling 9 freight cars, each of which is loaded with the same weight. The
mass of each loaded car is 37,000 kg, and we can neglect friction on these 9 cars. If the train
is accelerating forward at 0.81 m/s² on a level track, what is the tension in the coupling
between the second and third cars? (The car nearest the locomotive is counted as the first
car.)

Accepted Answer

The answer of A locomotive is pulling 9 freight cars,...

Question 4

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box
and the surface is 0.30, and the coefficient of kinetic friction is 0.20. What horizontal force
must be applied to the box to cause it to start sliding along the surface?

Accepted Answer

The answer of A 55-kg box rests on a horizontal...

Question 5

An object slides on a level floor. It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s². What is the coefficient of kinetic friction between the object and the floor?

Accepted Answer

The coefficient of kinetic friction ($\mu_k$) can be found using the formula $\mu_k = \frac{a}{g}$, where $a$ is the acceleration (2.4 m/s²) and $g$ is the acceleration due to gravity (approximately 9.8 m/s²). Thus, $\mu_k = \frac{2.4}{9.8} \approx 0.24$. The mass of the object is not needed because it cancels out in the equation for frictional force ($f = \mu_k \cdot m \cdot g$), making the coefficient of kinetic friction independent of mass.

Question 6

A policeman investigating an accident measures the skid marks left by a car on the horizontal road. He determines that the distance between the point that the driver slammed on the brakes
(thereby locking the wheels) and the point where the car came to a stop was 28.0 m. From a
Reference manual he determines that the coefficient of kinetic friction between the tires and the
Road under the prevailing conditions was 0.300. How fast was the car going when the driver
Applied the brakes?

Accepted Answer

The speed of the car when the brakes were applied can be calculated using the formula derived from the work-energy principle, $v = \sqrt{2ad}$, where $v$ is the velocity, $a$ is the acceleration (deceleration in this case), and $d$ is the distance. The deceleration $a$ can be found using the formula $a = \mu g$, where $\mu$ is the coefficient of kinetic friction (0.300) and $g$ is the acceleration due to gravity (approximately 9.8 m/s$^2$). Substituting the given values, $a = 0.300 \times 9.8 = 2.94$ m/s$^2$, and then calculating the velocity gives $v = \sqrt{2 \times 2.94 \times 28.0} \approx 12.8$ m/s.

Question 7

As shown in the figure, a 10-kg block on a perfectly smooth horizontal table is connected by a horizontal string to a 63-kg block that is hanging over the edge of the table. What is the magnitude
Of the acceleration of the 10-kg block when the other block is gently released?

Accepted Answer

The answer of As shown in the figure, a 10-kg...

Question 8

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are  5.0 kg, 3.0 kg, and  2.0 kg , with the  3.0-kg mass in the center. A force of  50 N pushes on the  5.0-kg box, which pushes against the other two boxes. What magnitude force does the  5.0-kg box exert on the  3.0-kg box?

Accepted Answer

The force exerted by the 5.0-kg box on the 3.0-kg box is equal to the force exerted by the 50 N force on the 5.0-kg box, which is 25 N.

Question 9

A bulldozer attempts to drag a log weighing 500 N along the rough horizontal ground.
The cable attached to the log makes an angle of 30° above the ground. The coefficient of
static friction between the log and the ground is 0.50, and the coefficient of kinetic friction
is 0.35. What minimum tension is required in the cable in order for the log to begin to
slide?

Accepted Answer

The answer of A bulldozer attempts to drag a log...

Question 10

A 50-kg box is being pushed along a horizontal surface. The coefficient of static friction between the box and the ground is 0.65, and the coefficient of kinetic friction is 0.35. What horizontal force
Must be exerted on the box for it to accelerate at 1.2 m/s²?

Accepted Answer

To find the force required to accelerate the box, we first calculate the force of static friction since it needs to be overcome to start moving the box. The force of static friction (F_static) is given by F_static = μ_static * N, where μ_static is the coefficient of static friction and N is the normal force. The normal force (N) is equal to the weight of the box, which is mass (m) times gravity (g), so N = m * g. For a 50-kg box, N = 50 kg * 9.8 m/s² = 490 N. Therefore, F_static = 0.65 * 490 N = 318.5 N.Once the box starts moving, we deal with kinetic friction to maintain acceleration. The force of kinetic friction (F_kinetic) is given by F_kinetic = μ_kinetic * N, where μ_kinetic is the coefficient of kinetic friction. So, F_kinetic = 0.35 * 490 N = 171.5 N.The net force (F_net) required to accelerate the box is the sum of the force to overcome kinetic friction and the force needed to accelerate the box at 1.2 m/s², given by Newton's second law, F = m * a, where a is the acceleration. So, the additional force needed for acceleration is F_acceleration = 50 kg * 1.2 m/s² = 60 N.Therefore, the total force required is F_total = F_kinetic + F_acceleration = 171.5 N + 60 N = 231.5 N, which rounds to 230 N, making E the correct answer.

Question 11

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a rope that goes over an ideal pulley. If the masses are gently released from rest, how long does it take for the 3.0-kg mass
To rise by 1.0 m?

Accepted Answer

The answer of A 3.0-kg mass and a 5.0-kg mass...

Question 12

A 50-kg box is resting on a horizontal floor. A force of 250 N directed at an angle of 30.0° below the horizontal is applied to the box. The coefficient of static friction between the box and the
Surface is 0.40, and the coefficient of kinetic friction is 0.30. What is the force of friction on the box?

Accepted Answer

The answer of A 50-kg box is resting on a...

Question 13

A 5.0-kg block and a 4.0-kg block are connected by a 0.6 kg rod, as shown in the figure.
The links between the blocks and the rod are denoted by A and B. A vertical upward force
of magnitude F is applied to the upper block. The blocks and rod assembly are moving
downward at constant velocity of 85 cm/s.
(a) What is the magnitude of the applied force F?
(b) What magnitude force does link A exert?

Accepted Answer

The answer of A 5.0-kg block and a 4.0-kg block...

Question 14

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley. If the masses are gently released, what is the resulting acceleration of the
Masses?

Accepted Answer

The answer of A 3.0-kg mass and a 5.0-kg mass...

Question 15

A 5.0-kg block and a 4.0-kg block are connected by a 0.6 kg rod, as shown in the figure.
The links between the blocks and the rod are denoted by A and B. A vertical upward force
of magnitude F of magnitude 150 N is applied to the upper block. What magnitude force
does each of the links A and B exert?

Accepted Answer

The answer of A 5.0-kg block and a 4.0-kg block...

Question 16

In the figure, block A has a mass of 3.00 kg. It rests on a smooth horizontal table and is connected by a very light horizontal string over an ideal pulley to block B, which has a mass of 2.00 kg. When
Block B is gently released from rest, how long does it take block B to travel 80.0 cm?

Accepted Answer

The answer of In the figure, block A has a...

Question 17

Three blocks, light connecting ropes, and a light frictionless pulley comprise a system, as
shown in the figure. An external force of magnitude P is applied downward on block A,
causing block A to accelerate downward at a constant 2.5 m/s². The tension in the rope
connecting block B and block C is equal to 60 N.
(a) What is the magnitude of the force P?
(b) What is the mass of block C?

Accepted Answer

The answer of Three blocks, light connecting ropes, and a...

Question 18

As shown in the figure, two blocks are connected by a very light string, and the upper block is pulled upward by a different string. The masses of the upper and lower blocks are  300 g and  240 g, respectively. The string between the blocks will break if its tension exceeds  3.6 N, and the string that pulls the combination upward will break if its tension exceeds  7.8 N.
(a) What is the largest upward acceleration that the blocks can be given without either string breaking?
(b) If the upward acceleration is slightly higher than this, which string breaks, the upper one or the lower one?

Accepted Answer

The answer of As shown in the figure, two blocks...

Question 19

The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30, respectively. What is the force of friction on the box when a 15-N horizontal push is
Applied to the box?

Accepted Answer

The answer of The coefficients of static and kinetic friction...

Question 20

A baseball player is running to second base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.180, and the
Coefficient of static friction is 3.14. What is his speed when he reaches the plate?

Accepted Answer

Explanation:The force of kinetic friction is:$$f_k=\mu_k n=\mu_k mg$$The work done by the force of kinetic friction is:$$W_f=-\mu_k mgd=-\mu_k mg(4.80	ext{ m})$$The change in kinetic energy is:$$\Delta K=K_f-K_i=\frac{1}{2}mv_f^2-\frac{1}{2}mv_i^2$$The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy:$$W_{net}=\Delta K$$Therefore,$$-\mu_k mgd=\frac{1}{2}mv_f^2-\frac{1}{2}mv_i^2$$Solving for $v_f$, we get:$$v_f=\sqrt{v_i^2-2\mu_k gd}=\sqrt{(5.03	ext{ m/s})^2-2(0.180)(9.81	ext{ m/s}^2)(4.80	ext{ m})}$$$$v_f=2.89	ext{ m/s}$$

Quiz 4: Dynamics: Newtons Laws of Motion

The figure shows a 100-kg block being released from rest from a height of 1.0 m. It then takes 0.53 s for it to reach the floor. What is the mass m of the block on the left? There is no friction or mass in The pulley, and the connecting rope is very light.

A 55-kg box rests on a horizontal surface. The coefficient of static friction between the box and the surface is 0.30, and the coefficient of kinetic friction is 0.20. What horizontal force must be applied to the box to cause it to start sliding along the surface?

An object slides on a level floor. It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s². What is the coefficient of kinetic friction between the object and the floor?

As shown in the figure, a 10-kg block on a perfectly smooth horizontal table is connected by a horizontal string to a 63-kg block that is hanging over the edge of the table. What is the magnitude Of the acceleration of the 10-kg block when the other block is gently released?

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg , with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg box, which pushes against the other two boxes. What magnitude force does the 5.0-kg box exert on the 3.0-kg box?

A 50-kg box is being pushed along a horizontal surface. The coefficient of static friction between the box and the ground is 0.65, and the coefficient of kinetic friction is 0.35. What horizontal force Must be exerted on the box for it to accelerate at 1.2 m/s²?

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a rope that goes over an ideal pulley. If the masses are gently released from rest, how long does it take for the 3.0-kg mass To rise by 1.0 m?

A 3.0-kg mass and a 5.0-kg mass hang vertically at the opposite ends of a very light rope that goes over an ideal pulley. If the masses are gently released, what is the resulting acceleration of the Masses?

In the figure, block A has a mass of 3.00 kg. It rests on a smooth horizontal table and is connected by a very light horizontal string over an ideal pulley to block B, which has a mass of 2.00 kg. When Block B is gently released from rest, how long does it take block B to travel 80.0 cm?

The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30, respectively. What is the force of friction on the box when a 15-N horizontal push is Applied to the box?

A baseball player is running to second base at 5.03 m/s. When he is 4.80 m from the plate he goes into a slide. The coefficient of kinetic friction between the player and the ground is 0.180, and the Coefficient of static friction is 3.14. What is his speed when he reaches the plate?