We change velocity by applying an acceleration, which is a change in either speed or direction, or both.
Understanding Velocity Change
Velocity, a vector quantity, describes both an object's speed and its direction. Therefore, changing the velocity of an object means altering either its speed, its direction, or both. This alteration is caused by acceleration.
Ways to Change Velocity
Here's a breakdown of how to change velocity:
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Changing Speed: This is perhaps the most intuitive way to change velocity. If an object is moving at a certain speed, increasing or decreasing that speed will change its velocity. For example, a car accelerating from a stop is changing its velocity.
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Changing Direction: Even if the speed of an object remains constant, changing its direction will change its velocity. Imagine a car moving at a constant speed around a circular track. While its speed is constant, its direction is constantly changing, meaning its velocity is also constantly changing.
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Changing Both Speed and Direction: In many real-world scenarios, both speed and direction change simultaneously. For instance, an airplane taking off increases its speed and changes its direction upwards.
Acceleration: The Key to Velocity Change
Acceleration is defined as the rate of change of velocity over time. Mathematically, it's expressed as:
Acceleration = (Change in Velocity) / (Change in Time)This means that any force that causes an object to accelerate will change its velocity. Forces such as gravity, friction, and applied forces can all contribute to acceleration and, therefore, changes in velocity.
Examples
- A ball thrown upwards: Gravity causes the ball to decelerate (decrease its upward speed) and eventually change direction, accelerating downwards.
- A car braking: The brakes apply a force that causes the car to decelerate, changing its velocity.
- A satellite orbiting Earth: While the satellite's speed might be relatively constant, its direction is constantly changing as it moves in a circle around the Earth, meaning its velocity is also constantly changing due to the gravitational force.
In summary, velocity is changed through acceleration, which manifests as a change in speed, direction, or both.
