Calculate the magnitude of the average net force on the car

In summary, the conversation discusses a car coasting on a road and its decrease in speed after crossing a sandy section. It asks whether the net work done on the car is positive, negative, or zero, and also calculates the magnitude of the average net force on the car in the sandy section. The solution involves using the equation for work and understanding the relationship between kinetic energy and work. The conversation ends with the successful calculation of the average net force.
  • #1
Chrisleo13
28
0

Homework Statement



A 1270-kg car coasts on a horizontal road with a speed of 18.1 m/s. After crossing an unpaved, sandy stretch of road 28.4 m long, its speed decreases to 11.3 m/s. Was the net work done on the car positive, negative, or zero?

b. Calculate the magnitude of the average net force on the car in the sandy section.


Homework Equations


W = F(delta r)(cos theta)


The Attempt at a Solution


I started looking at it. I understand work but for some reason I am stuck here.
 
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  • #2
Well look at it this way, initially you consider all of its energy to be kinetic. Once it begins to cross the sand, some of it's kinetic energy is transcribed into work:

[tex] \frac{1}{2}mv_1^2 = \frac{1}{2}mv_2^2 + F\Delta d [/tex]

Mass remains constant, and we are told that [tex] v_2 [/tex] decreases, that implies that work; [tex] F\Delta d [/tex] is positive (or else the equation would not be balanced).

For part b) you just need to solve the equation listed above. You have everything except F.
 
  • #3
Alright, I got it. Thanks.
 

What does "magnitude of the average net force" mean?

The magnitude of the average net force refers to the strength or intensity of the overall force acting on an object. It is calculated by finding the sum of all the forces acting on the object and taking into account their direction.

How do you calculate the magnitude of the average net force on a car?

To calculate the magnitude of the average net force on a car, you need to first determine all the forces acting on the car, including the force of gravity, friction, and any applied forces. Then, you can use the formula Fnet = ma, where Fnet is the net force, m is the mass of the car, and a is the acceleration of the car. The magnitude of the average net force will be the absolute value of the resulting value.

Why is it important to calculate the magnitude of the average net force on a car?

Calculating the magnitude of the average net force on a car is important because it allows us to understand the overall effect of all the forces acting on the car. This information is crucial for predicting the motion of the car and determining if it will accelerate, decelerate, or maintain a constant speed.

What units are used to measure the magnitude of the average net force?

The magnitude of the average net force is typically measured in Newtons (N), which is the standard unit of force in the International System of Units (SI). However, other units such as pounds (lb) or kilograms-force (kgf) may also be used depending on the context.

Can the magnitude of the average net force on a car be negative?

Yes, the magnitude of the average net force on a car can be negative. This indicates that the net force is acting in the opposite direction to the motion of the car. A negative magnitude does not necessarily mean the car is moving backwards, but rather that the forces acting on it are causing it to decelerate or slow down.

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