# Calculate the time at which the object changes direction

• Snipes
In summary, the object in the given scenario starts from rest and accelerates uniformly to a velocity of 20.0 m/s in 5.0 minutes, maintains a constant speed for the next 10 minutes, and then accelerates in the opposite direction to reach a velocity of 15 m/s in 3.0 minutes. Using the equations y=mx+b and v=d/t, the student attempted to find the time at which the object changes direction by creating a velocity-time graph. However, they encountered some confusion in finding the equation y=mx+b and determining the displacement as the object crosses the x-axis and moves into negative. A possible error in rounding down the acceleration value may have led to a slightly different answer.
Snipes

## Homework Statement

An object starts from rest and uniformly acquires a velocity of 20.0 m/s in 5.0 minutes. For the next 10. minutes the object moves with a constant speed. After 10. minutes moving at 20. m/s the object then again accelerates and reaches a speed of 15 m/s in the opposite direction in 3.0 minutes time.

Calculate the time at which the object changes direction

y=mx+b
v=d/t

## The Attempt at a Solution

made velocity time graph. tried to find the equation y=mx + b. already knew that slope + -.19 unknown what b is and i found that velocity = 0 when time is at 1005.275 seconds however it said this was wrong. I am very confused and jumbled. Unsure how to find displacement since it crosses the x-axis and moves into negative.

Snipes said:

## Homework Statement

An object starts from rest and uniformly acquires a velocity of 20.0 m/s in 5.0 minutes. For the next 10. minutes the object moves with a constant speed. After 10. minutes moving at 20. m/s the object then again accelerates and reaches a speed of 15 m/s in the opposite direction in 3.0 minutes time.

Calculate the time at which the object changes direction

y=mx+b
v=d/t

## The Attempt at a Solution

made velocity time graph. tried to find the equation y=mx + b. already knew that slope + -.19 unknown what b is and i found that velocity = 0 when time is at 1005.275 seconds however it said this was wrong. I am very confused and jumbled. Unsure how to find displacement since it crosses the x-axis and moves into negative.

Could you post image of your graph ?

I am getting value of time which is slightly lesser than what you are getting .

Last edited:
Merlin3189
When you calculated the acceleration did you get a figure of -0.194444m/s^2. If so don't round it down to -0.19m/s^2 for the next step as that seems to account for your slightly different answer to the one I get.

## 1. How do you calculate the time at which an object changes direction?

To calculate the time at which an object changes direction, you need to know the initial velocity and acceleration of the object. You can then use the formula t = (v - u)/a, where t is the time, v is the final velocity, u is the initial velocity, and a is the acceleration.

## 2. What factors affect the time at which an object changes direction?

The time at which an object changes direction is affected by the initial velocity, acceleration, and mass of the object. Other external factors such as air resistance and friction may also play a role in determining the time at which an object changes direction.

## 3. Can the time at which an object changes direction be negative?

No, the time at which an object changes direction cannot be negative. Time is always a positive quantity and represents the duration of an event.

## 4. How does the angle of the object's initial velocity affect the time at which it changes direction?

The angle of the object's initial velocity does not directly affect the time at which it changes direction. However, the direction of the initial velocity can impact the acceleration, which in turn affects the time at which the object changes direction.

## 5. Is it possible to calculate the time at which an object changes direction without knowing the initial velocity?

No, it is not possible to calculate the time at which an object changes direction without knowing the initial velocity. The initial velocity is a crucial component in determining the time at which an object changes direction.

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