/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 91 Suppose you are sitting in a car... [FREE SOLUTION] | 91影视

91影视

Log out

Learning Materials

Features

Discover

Chapter 6: Problem 91

Suppose you are sitting in a car that is speeding up. Assume the car has rear-wheel drive. (a) Draw free-body diagrams for your own body, the seat in which you are sitting (apart from the car), the car (apart from the seat), and the road surface where the tires and the road interact. (b) Describe each force in words; show larger forces with longer arrows. (c) Identify the third-law pairs of forces. (d) Explain carefully in your own words the origin of the force imparting acceleration to the car.

Short Answer

Expert verified
Draw FBDs for your body, the seat, the car, and the road. Identify all forces and third-law pairs. The car accelerates via friction at the rear wheels.

Step by step solution

01

- Draw Free-Body Diagram for Your Own Body

Draw a diagram representing your body. Indicate forces acting on it: gravity pointing downwards, normal force pointing upwards, friction force pointing backwards due to the seat, and if the car is enclosed, forward force from the seat back.
02

- Draw Free-Body Diagram for the Seat

Draw a diagram of the seat. Mark forces such as the gravitational force acting downwards, the normal force from the car acting upwards, and the backward frictional force from your body.
03

- Draw Free-Body Diagram for the Car

Draw a diagram of the car excluding the seat. Show forces like the gravitational force acting downwards, the normal force from the road acting upwards, the frictional force from the rear tires acting forward, and the air resistance acting backward.
04

- Draw Free-Body Diagram for the Road

Draw a segment of the road surface. Indicate forces such as the normal force acting upwards from where the tires exert force downwards and the backward frictional force that propels the car forward.
05

- Describe Each Force

For each diagram, describe the forces identified: - For your body: gravity, normal force, and friction from the seat.- For the seat: gravity, normal force, friction from your body.- For the car: gravity, normal force, friction from the tires and air resistance.- For the road: normal force and frictional force.
06

- Identify Third-Law Force Pairs

Identify corresponding Newton's third law pairs: - The force your body exerts on the seat and the seat's reaction force on your body.- The force the car tires exert on the road and the road's reaction force on the car tires.- The force of gravity on the car and the normal force from the road.
07

- Explain the Origin of the Acceleration Force

The force imparting acceleration to the car originates from the engine and is transferred to the rear wheels. The frictional force between the rear tires and the road surface provides the forward force that accelerates the car.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

Key Concepts

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

Newton's Third Law
Newton's third law states that for every action, there is an equal and opposite reaction. This is crucial when analyzing forces in the given exercise. When you sit in the accelerating car, the seat pushes you forward. At the same time, your body pushes back on the seat with equal force but in the opposite direction.
Another example is the interaction between the car鈥檚 tires and the road. The tires push backward against the road, and the road pushes the tires forward, which propels the car.
Always remember that action-reaction force pairs act on different objects but are equal in magnitude and opposite in direction.
Gravitational Force
Gravitational force is the force that attracts objects toward the center of the Earth. It is always acting downward.
In the context of the exercise:
  • Your body experiences a downward gravitational force.
  • The seat experiences a downward gravitational force.
  • The car also has a gravitational force acting on it, pulling it toward the Earth.
These gravitational forces are balanced by normal forces acting upwards from the ground, seat, or car.
Frictional Force
Frictional force opposes the motion of objects in contact. It is essential for providing traction.
For your body, friction from the seat resists your backward motion. For the seat, backward friction comes from your body. For the car, the rear tires generate friction against the road's surface, propelling the car forward.
Without frictional force, the car wouldn't move forward, as the tires would simply spin in place.
Normal Force
Normal force is the support force exerted upon an object in contact with another stable object.
In your scenario:
  • Your body's normal force is the seat pushing up against you, counteracting gravity.
  • The seat鈥檚 normal force comes from the car pushing it upward.
  • The car鈥檚 normal force is the upward force from the road, balancing the car鈥檚 weight.
  • The road's normal force is directed upward where the car's tires press down.
Normal forces are perpendicular to the surfaces in contact.
Acceleration
Acceleration is the rate of change of velocity. In this exercise, the car accelerates as it speeds up.
The force causing the car's acceleration originates from the engine. This force is transmitted to the rear wheels.
Due to the frictional force between the tires and the road surface, the car moves forward. Your body is also accelerated forward by the normal force from the seat.
Always consider all forces acting on each object to understand how acceleration occurs.

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

A bolt is threaded onto one end of a thin horizontal rod, and the rod is then rotated horizontally about its other end. An engineer monitors the motion by flashing a strobe lamp onto the rod and bolt, adjusting the strobe rate until the bolt appears to be in the same eight places during each full rotation of the rod (Fig. 6-75). The strobe rate is 2000 flashes per second; the bolt has mass \(30 \mathrm{~g}\) and is at radius \(3.5 \mathrm{~cm}\). What is the magnitude of the force on the bolt from the rod?

A young man is pushing a baby carriage at a constant velocity along a level street. A friend comes by to chat and the young man lets go of the carriage. It rolls on for a bit, slows, and comes to a stop. At time \(t=0\) the young man is walking with a constant velocity. At time \(t_{1}\) he releases the carriage. At time \(t_{2}\) the carriage comes to rest. Sketch qualitatively accurate (i.e., we don't care about the values but we do care about the shape) graphs of each of the following variables versus time: (a) position of the carriage, (b) velocity of the carriage, (c) acceleration of the carriage, (d) net force on the carriage, (e) force the man exerts on the carriage, (f) force of friction on the carriage. Be sure to note the important times \(t=0, t_{1}\), and \(t_{2}\) on the time axes of your graphs. Take the positive direction to be the direction in which the man was initially walking.

Two horizontal forces act on a \(2.0 \mathrm{~kg}\) chopping block that can slide over a frictionless kitchen counter, which lies in an \(x y\) plane. One force is \(\vec{F}_{A}=(3.0 \mathrm{~N}) \hat{\mathrm{i}}+(4.0 \mathrm{~N}) \hat{\mathrm{j}}\). Find the acceleration of the chopping block in unit-vector notation when the other force is (a) \(\vec{F}_{B}=(-3.0 \mathrm{~N}) \hat{\mathrm{i}}+(-4.0 \mathrm{~N}) \hat{\mathrm{j}}\), (b) \(\vec{F}_{B}=(-3.0 \mathrm{~N}) \hat{\mathrm{i}}+\) \((4.0 \mathrm{~N}) \hat{\mathrm{j}}\), and \((\mathrm{c}) \vec{F}_{B}=(3.0 \mathrm{~N}) \hat{\mathrm{i}}+(-4.0 \mathrm{~N}) \hat{\mathrm{j}}\).

Luggage is transported from one location to another in an airport by a conveyor belt. At a certain location, the belt moves down an incline that makes an angle of \(2.5^{\circ}\) with the horizontal. Assume that with such a slight angle there is no slipping of the luggage. Determine the magnitude and direction of the frictional force by the belt on a box weighing \(69 \mathrm{~N}\) when the box is on the inclined portion of the belt for the following situations: (a) The belt is stationary. (b) The belt has a speed of \(0.65 \mathrm{~m} / \mathrm{s}\) that is constant. (c) The belt has a speed of \(0.65 \mathrm{~m} / \mathrm{s}\) that is increasing at a rate of \(0.20 \mathrm{~m} / \mathrm{s}^{2}\). (d) The belt has a speed of \(0.65 \mathrm{~m} / \mathrm{s}\) that is decreasing at a rate of \(0.20 \mathrm{~m} / \mathrm{s}^{2}\). (e) The belt has a speed of \(0.65 \mathrm{~m} / \mathrm{s}\) that is increasing at a rate of \(0.57 \mathrm{~m} / \mathrm{s}^{2}\).

A high-speed railway car goes around a flat, horizontal circle of radius \(470 \mathrm{~m}\) at a constant speed. The magnitudes of the horizontal and vertical components of the force of the car on a \(51.0 \mathrm{~kg}\) passenger are \(210 \mathrm{~N}\) and \(500 \mathrm{~N}\), respectively. (a) What is the magnitude of the net force (of all the forces) on the passenger? (b) What is the speed of the car?
See all solutions

Recommended explanations on Physics Textbooks

Conservation of Energy and Momentum

Read Explanation

Fundamentals of Physics

Read Explanation

Famous Physicists

Read Explanation

Electromagnetism

Read Explanation

Electric Charge Field and Potential

Read Explanation

Classical Mechanics

Read Explanation
View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.