Calculating Friction Force from Velocity Equation

In summary, a 12 kg box with an initial velocity of +8.4 m/s slides across the floor and comes to a stop after sliding +13.8m. To find the friction present, the equations f=ma and v^2=v(o)^2+2ad were used. The resulting acceleration was -2.55 m/s^2, leading to a frictional force of -2242.06 N, which can be negative if the displacement is taken as positive due to its opposite direction to the motion. After checking the math, it was determined that the correct mass of the box is 12 kg.
  • #1
mrphobio
27
0

Homework Statement


A 12 kg box slides across the floor with an initial velocity of +8.4 m/s. It comes to a stop after sliding +13.8 m.

How much friction was present?


Homework Equations


f=ma v^2=v(o)^2+2ad


The Attempt at a Solution


I did the ''v^2" equation to find out what the acceleration was, so i could find out what F equaled in f=ma. I got -2.55=a. I plugged that into F=ma, F=877(-2.55), which then F=-2242.06. But can a force be negative? And also from there I'm completely lost.
 
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  • #2
Frictional force will be negative if you choose the displacement as positive because it is acting opposite to the direction of motion.

Check your math. Where did you get 877 for the mass?? It says 12kg.
 
  • #3
Well. There we go it worked. I have not a clue where I got that 877. Sometimes another pair of eyes helps a lot haha
 

Related to Calculating Friction Force from Velocity Equation

1. What is F=ma and Velocity equation?

F=ma and Velocity equation is a fundamental equation in physics that describes the relationship between force, mass, and acceleration. It states that the force applied to an object is equal to its mass multiplied by its acceleration.

2. How is F=ma and Velocity equation used in real life?

F=ma and Velocity equation is used in various real-life applications, such as calculating the thrust of a rocket, determining the force needed to lift an object, and understanding the motion of objects in sports like baseball and football.

3. What is the significance of F=ma and Velocity equation?

F=ma and Velocity equation is significant because it helps us understand the behavior of objects in motion and allows us to make predictions about their future movements. It is also the basis for many other important equations in physics.

4. What is the relationship between F=ma and Velocity equation?

The F=ma equation and the equation for velocity (v = u + at) are closely related, as they both involve acceleration. The F=ma equation gives us the force needed to produce a certain acceleration, while the velocity equation tells us the speed an object will reach after a given time with a specific acceleration.

5. How do you solve problems using F=ma and Velocity equation?

To solve problems using F=ma and Velocity equation, you first need to identify the known values of force, mass, and acceleration. Then, you can use the equation to calculate the missing value. It is essential to use consistent units of measurement and pay attention to the direction of the force and acceleration vectors.

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