Calculating Velocity/Speed of a Lost Coin

  • Thread starter cbrowne
  • Start date
In summary: I like to keep one more significant figure than is justified, so I would give my final answer as vave = 0.047 m/s and save the rest of the digits for the calculation.In summary, the child's total displacement was -24.1 m. Her average velocity was 0.047 m/s, and her average speed was 0.059 m/s. It is important to use the correct units and significant figures when solving problems like this.
  • #1
cbrowne
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Hello could someone please check this question for me. Thanks


Homework Statement





On her way to school, a child discovered that her loonie is missing and there is a
hole in her pocket. In searching for the missing coin, the child turned back and
walked for 9.5 m, along the sidewalk. Then she turned forward and walked for
3.2 m and then turned back again and walked for 17.8 m before finding her
loonie.
(a) What is the total displacement of the child?
(b) If the child spent 8.5 minutes searching for the coin, what was her average velocity? (c) What was her average speed?

Homework Equations





The Attempt at a Solution



a) Δ x = -24.1 m

b) V average = Δx/ Δt = -24.1m/ 8.5 min x 60 secs = 0.047255 m /s

c) S avg = d1+d2+d3/ Δt

S avg = 9.5m+ 3.2m + 17.8 m/8.5min x 60 secs = 0.059804 m/s
 
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  • #2
Your answers look good mathematically. I do have 2 comments:

1. For the time conversions, you should use 60 sec/min, not 60 sec. Doesn't change the number, but it makes a difference in the units you get and how you think about the units.

2. We know the distances and times to just 2 or 3 significant figures. So your final answers are given to a lot more accuracy than is justified.
 
  • #3


Your calculations for the total displacement and average velocity are correct. However, for average speed, you should divide the total distance (9.5 m + 3.2 m + 17.8 m = 30.5 m) by the total time (8.5 min x 60 secs = 510 s). So the correct answer for average speed would be 30.5 m / 510 s = 0.059804 m/s. Good job on the calculations!
 

What is the difference between velocity and speed?

Velocity and speed are often used interchangeably, but they actually have different meanings in physics. Speed is the rate at which an object travels, while velocity is the rate at which an object travels in a specific direction. In other words, velocity includes both speed and direction.

How is velocity calculated?

Velocity is calculated by dividing the displacement of an object by the time it took to travel that distance. This can be represented by the equation v = d/t, where v is velocity, d is displacement, and t is time. Velocity is typically measured in distance per unit time, such as meters per second or kilometers per hour.

What is the difference between average velocity and instantaneous velocity?

Average velocity is the total displacement of an object divided by the total time it took to travel that distance. This is a representation of the overall motion of the object. Instantaneous velocity, on the other hand, is the velocity of an object at a specific moment in time. It is calculated by taking the limit of the average velocity as the time interval approaches zero.

Can an object have a constant speed but changing velocity?

Yes, an object can have a constant speed but changing velocity. This occurs when the object is moving in a circular path. The speed may remain constant, but the direction of the object's velocity is constantly changing as it moves around the circle. This means that the velocity is changing, even though the speed remains the same.

How does velocity affect an object's motion?

Velocity plays a crucial role in determining an object's motion. The direction of an object's velocity determines its direction of motion, while the magnitude of its velocity determines its speed. Additionally, changes in velocity, such as acceleration or deceleration, can cause changes in an object's motion, including changes in speed and direction.

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