Solving for time | One-dimensional motion | Physics | Khan Academy

TL;DR

Learn how to calculate the time it takes for an object to travel a certain distance given its velocity and direction.

Transcript

Let's work through another few scenarios involving displacement, velocity, and time, or distance, rate, and time. So over here we have, Ben is running at a constant velocity of three 3 meters per second to the east. And just as a review, this is a vector quantity. They're giving us the magnitude and the direction. If they just said 3 meters per sec... Read More

Key Insights

• ⌛ Displacement, velocity, and time are vector quantities that involve both magnitude and direction.
• 🐎 Speed is a scalar quantity that only considers the magnitude of motion, while velocity is a vector quantity that takes into account both the magnitude and the direction of motion.
• ⌛ The formula distance = rate × time is used to calculate time when working with scalar quantities, while displacement = velocity × time is used for vector quantities.
• 🧘 Displacement is the change in position of an object and can be positive or negative depending on the direction.
• 🗂️ Vector quantities can be manipulated algebraically by multiplying or dividing them to solve for different variables.
• ☠️ Time can be calculated by dividing displacement or distance by velocity or rate.
• 🦻 Choosing a convention to define positive and negative directions can simplify calculations and aid in interpreting results.

Questions & Answers

Q: What is the difference between speed and velocity?

Speed is a scalar quantity that only considers the magnitude of motion, while velocity is a vector quantity that takes into account both the magnitude and the direction of motion.

Q: How can you calculate time given displacement and velocity?

You can use the formula time = displacement / velocity, where displacement is the distance traveled in a specific direction and velocity is the rate of motion in that direction.

Q: Can you explain the concept of vector quantities?

Vector quantities have both magnitude and direction, such as displacement and velocity. These quantities are represented using arrows or bold letters to indicate their direction and can be added or subtracted algebraically.

Q: Why is it important to consider direction when calculating time?

Considering direction is crucial because time is affected by whether an object is moving towards or away from a reference point. Calculations involving displacement, velocity, and time need to be done with respect to the specified direction.

Summary & Key Takeaways

• Displacement, velocity, and time are vector quantities that involve both magnitude and direction.

• To calculate time, you can use the formula distance = rate × time or displacement = velocity × time, depending on whether you are working with scalar or vector quantities.

• In this example, Ben is running at a constant velocity of 3 meters per second to the east, and it will take him 240 seconds to travel 720 meters in that direction.