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A 6.00-kg box sits on a ramp that is inclined at 37.0\(^\circ\) above the horizontal. The coefficient of kinetic friction between the box and the ramp is \(\mu_k\) = 0.30. What \(horizontal\) force is required to move the box up the incline with a constant acceleration of 3.60 m/s\(^2\)?

Short Answer

Expert verified
The required horizontal force is approximately 88.67 N.

Step by step solution

01

Identify Forces Involved

First, identify all forces acting on the box. These include the gravitational force, the normal force, the frictional force, and the horizontal applied force that we need to find.
02

Resolve Gravitational Force

The gravitational force can be resolved into two components: one parallel to the incline \( (mg \sin \theta) \) and one perpendicular to it \( (mg \cos \theta) \). Here, \( g = 9.8 \text{ m/s}^2 \), \( m = 6.00 \text{ kg} \) and \( \theta = 37.0^\circ \).
03

Calculating Normal Force

The normal force \( N \) is equal to the component of the gravitational force perpendicular to the incline: \( N = mg \cos \theta \). Substitute the known values: \( N = 6.00 \times 9.8 \times \cos(37.0^\circ) \approx 47.04 \text{ N} \).
04

Calculate Frictional Force

The frictional force \( f_k \) is given by \( f_k = \mu_k N \). With \( \mu_k = 0.30 \), substitute \( N \) from the previous step: \( f_k = 0.30 \times 47.04 = 14.11 \text{ N} \).
05

Net Force Equation

The net force required to accelerate the box up the incline can be given by: \( F_{net} = F_{applied} - (mg \sin \theta + f_k) = ma \). Using \( a = 3.60 \text{ m/s}^2 \), substitute the known values: \( F_{applied} - (6.00 \times 9.8 \times \sin(37.0^\circ) + 14.11) = 6.00 \times 3.60 \).
06

Solve for Applied Force

Calculate \( F_{applied} \) from the equation: \( F_{applied} = 6.00 \times 3.60 + 6.00 \times 9.8 \times \sin(37.0^\circ) + 14.11 \). Calculating each part: \( 6.00 \times 3.60 = 21.6 \), \( 6.00 \times 9.8 \times \sin(37.0^\circ) \approx 35.3 \), and \( 21.6 + 35.3 + 14.11 \approx 71.01 \text{ N} \).
07

Calculate Horizontal Force

To find the horizontal component \( F_{horizontal} \), use trigonometry: \( F_{horizontal} = \frac{F_{applied}}{\cos(37.0^\circ)} \). Thus, \( F_{horizontal} = \frac{71.01}{\cos(37.0^\circ)} \approx 88.67 \text{ N} \).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Inclined Plane
An inclined plane, often called a ramp, is a flat surface tilted at an angle relative to a horizontal surface. When an object like a box is placed on an inclined plane, it is subjected to gravitational forces that act in specific ways. The gravitational force can be split into two components:
  • Parallel Component: This pulls the box down the slope and is calculated as \( mg \sin \theta \), where \( m \) is the mass of the object, \( g \) is the acceleration due to gravity, and \( \theta \) is the angle of the incline.
  • Perpendicular Component: This presses the box into the surface of the ramp and is considered when calculating the normal force. It's given by \( mg \cos \theta \).
Recognizing these components is crucial for analyzing the forces on objects in a physics problem involving inclined planes. Understanding an inclined plane helps us see how gravity affects movement along non-horizontal surfaces.
Kinetic Friction
Kinetic friction occurs when two surfaces are in motion relative to each other. In our exercise, it acts against the movement of the box on the ramp. The kinetic frictional force can be calculated using the equation:
  • \( f_k = \mu_k N \)
Where:
  • \( f_k \) is the kinetic friction force.
  • \( \mu_k \) is the coefficient of kinetic friction, indicative of how much friction exists between the two surfaces.
  • \( N \) is the normal force, the perpendicular force exerted by a surface to support the weight of the object resting on it.
In this case, the kinetic friction is calculated as 14.11 N, opposing the motion of the box as it slides up the inclined plane. It's vital to consider because it can significantly affect how much force is needed to achieve a certain motion.
Applied Force
An applied force is any force that is exerted on an object by a person or another object. In the scenario given, an external horizontal force is applied to move the box up the incline with constant acceleration. To determine the amount of applied force required, we must account for the:
  • Parallel component of gravitational force pulling the box down the incline.
  • Kinetic friction opposing the upward motion.
  • Desired net force needed to accelerate the box up the ramp.
The equation used is:
  • \( F_{applied} - (mg \sin \theta + f_k) = ma \)
The applied force must overcome both the friction and the slope’s gravitational pull to achieve the acceleration specified. This highlights the interplay of multiple forces and how they affect movement.
Acceleration
Acceleration refers to the rate of change of velocity of an object. It is a vector quantity, meaning it has both magnitude and direction. In our scenario, the box is required to accelerate up the ramp at 3.60 m/s\(^2\). Achieving this involves ensuring the net force acting on the box is calculated correctly.Newton’s second law (
  • \( F = ma \)
) plays a crucial role here. This states that the net force \( F \) required to accelerate an object of mass \( m \) by an acceleration \( a \) has to equal the product of the mass and the acceleration. In simpler terms, more force is needed to accelerate heavier objects or achieve faster acceleration.When calculating, it is essential to consider all acting forces including the gravitational pull, friction, and applied forces to get the correct resultant acceleration. Clarifying these force interactions helps ensure the correct application of physics concepts in real-world situations.

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Most popular questions from this chapter

A box with mass 10.0 kg moves on a ramp that is inclined at an angle of 55.0\(^\circ\) above the horizontal. The coefficient of kinetic friction between the box and the ramp surface is \(\mu_k =\) 0.300. Calculate the magnitude of the acceleration of the box if you push on the box with a constant force \(F =\) 120.0 N that is parallel to the ramp surface and (a) directed down the ramp, moving the box down the ramp; (b) directed up the ramp, moving the box up the ramp.

A 40.0-kg packing case is initially at rest on the floor of a 1500-kg pickup truck. The coefficient of static friction between the case and the truck floor is 0.30, and the coefficient of kinetic friction is 0.20. Before each acceleration given below, the truck is traveling due north at constant speed. Find the magnitude and direction of the friction force acting on the case (a) when the truck accelerates at 2.20 m/s\(^2\) northward and (b) when it accelerates at 3.40 m/s\(^2\) southward.

On the ride "Spindletop" at the amusement park Six Flags Over Texas, people stood against the inner wall of a hollow vertical cylinder with radius 2.5 m. The cylinder started to rotate, and when it reached a constant rotation rate of 0.60 rev/s, the floor dropped about 0.5 m. The people remained pinned against the wall without touching the floor. (a) Draw a force diagram for a person on this ride after the floor has dropped. (b) What minimum coefficient of static friction was required for the person not to slide downward to the new position of the floor? (c) Does your answer in part (b) depend on the person's mass? (\(Note\): When such a ride is over, the cylinder is slowly brought to rest. As it slows down, people slide down the walls to the floor.)

One problem for humans living in outer space is that they are apparently weightless. One way around this problem is to design a space station that spins about its center at a constant rate. This creates "artificial gravity" at the outside rim of the station. (a) If the diameter of the space station is 800 m, how many revolutions per minute are needed for the "artificial gravity" acceleration to be 9.80 m/s\(^2\)? (b) If the space station is a waiting area for travelers going to Mars, it might be desirable to simulate the acceleration due to gravity on the Martian surface (3.70 m/s\(^2\)). How many revolutions per minute are needed in this case?

A light rope is attached to a block with mass 4.00 kg that rests on a frictionless, horizontal surface. The horizontal rope passes over a frictionless, massless pulley, and a block with mass \(m\) is suspended from the other end. When the blocks are released, the tension in the rope is 15.0 N. (a) Draw two free-body diagrams: one for each block. (b) What is the acceleration of either block? (c) Find \(m\). (d) How does the tension compare to the weight of the hanging block?

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