Laws of motion magnitude of average acceleration

In summary: Remember, practice makes perfect!In summary, the conversation discusses finding the magnitude of the average acceleration of a rock that starts at 5.0 m/s, moves 3.0m in a straight line, and then stops. The correct formula for average acceleration is change in velocity over change in time, but the individual initially used the incorrect formula of change in displacement over change in time. After some guidance, they were able to correctly find the average acceleration to be 4.2 m/s^2.
  • #1
maxiJ
4
0

Homework Statement


A rock is rolled in the sand. It starts at 5.0 m/s, moves in a straight line for a distance of 3.0m and then stops. What is the magnitude of the average acceleration?

Homework Equations


aavg = change in V/ change in time
magnitude of acceleration = change of speed/time interval.

The Attempt at a Solution


i think i am thinking too hard about this problem. seems simple but cannot get the right answer
found time = 1.67 s and tried to plug in for average acceleration. 5.0/1.67 = 2.99 m/s^2
the correct answer is 4.2 m/s^2.
?? can't figure out what i am doing wrong.
 
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  • #2
maxiJ said:

Homework Statement


A rock is rolled in the sand. It starts at 5.0 m/s, moves in a straight line for a distance of 3.0m and then stops. What is the magnitude of the average acceleration?

Homework Equations


aavg = change in V/ change in time
magnitude of acceleration = change of speed/time interval.

The Attempt at a Solution


i think i am thinking too hard about this problem. seems simple but cannot get the right answer
found time = 1.67 s and tried to plug in for average acceleration. 5.0/1.67 = 2.99 m/s^2
the correct answer is 4.2 m/s^2.
?? can't figure out what i am doing wrong.
Welcome to Physics Forums,

Tell me, how did you find the time?
 
  • #3
thanks =)

i took 5.0 m/s and divided by the distance of 3.0 m to get 1.67 seconds.
so the ball traveled 3.0 m in 1.67 s at 5.0 m/s.
 
  • #4
maxiJ said:
thanks =)

i took 5.0 m/s and divided by the distance of 3.0 m to get 1.67 seconds.
so the ball traveled 3.0 m in 1.67 s at 5.0 m/s.
I'm afraid that's incorrect, it would be correct if 5.0m/s was the average velocity, but it isn't it's the initial velocity.

Do you know any kinematics equations?
 
  • #5
ah, yes.. i overlooked that.

well for average velocity its change in displacement over change in time, i think.
 
  • #7
wow that was a lot easier than i made it out to be. thanks for the help.
 
  • #8
maxiJ said:
wow that was a lot easier than i made it out to be. thanks for the help.
My pleasure.
 

FAQ: Laws of motion magnitude of average acceleration

1. What are the three laws of motion?

The three laws of motion were first described by Sir Isaac Newton in his work "Principia Mathematica" and they are:
1. An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.
2. The force applied to an object is equal to its mass multiplied by its acceleration.
3. For every action, there is an equal and opposite reaction.

2. What is the magnitude of average acceleration?

The magnitude of average acceleration is the change in velocity divided by the time interval over which the change occurred. It is a measure of how quickly an object's velocity is changing.

3. How is average acceleration calculated?

Average acceleration is calculated by taking the change in velocity and dividing it by the time interval. The formula for average acceleration is:
a = (vf - vi) / t
Where a is average acceleration, vf is final velocity, vi is initial velocity, and t is time.

4. How do the laws of motion relate to the magnitude of average acceleration?

The second law of motion states that the force applied to an object is equal to its mass multiplied by its acceleration. This means that the greater the force applied to an object, the greater its acceleration will be. This is why the laws of motion are important in understanding the magnitude of average acceleration.

5. What is the significance of understanding the laws of motion and average acceleration?

Understanding the laws of motion and average acceleration is crucial in many scientific fields, such as physics and engineering. It allows us to predict and analyze the motion of objects, and to design and build structures and machines that can withstand certain forces and accelerations. It also helps us understand the natural world and the behavior of objects in motion.

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