Chapter 10 Section 2

Acceleration and Motion 2 Acceleration and Motion Acceleration is the change in velocity divided by the time it takes for the change to occur. Acceleration has a direction. If an object speeds up, the acceleration is in the direction that the object is moving.

Acceleration and Motion 2 Acceleration and Motion If an object slows down, the acceleration is opposite to the direction that the object is moving. If the direction of the acceleration is at an angle to the direction of motion, the direction of motion will turn toward the direction of the acceleration.

When the speed of an object increases, it is accelerating. Acceleration 2 Speeding Up When an object that is already in motion speeds up, it also is accelerating. When the speed of an object increases, it is accelerating. The toy car is accelerating to the right. Its speed is increasing.

Acceleration 2 Slowing Down Acceleration occurs when an object slows down, as well as when it speeds up. The car is slowing down. During each time interval, the car travels a smaller distance, so its speed is decreasing.

Motion is not always along a straight line. Acceleration 2 Changing Direction Motion is not always along a straight line. If the acceleration is at an angle to the direction of motion, the object will turn. At the same time, it might speed up, slow down, or not change speed at all.

Motion is not always along a straight line. Acceleration 2 Changing Direction Motion is not always along a straight line. If the acceleration is at an angle to the direction of motion, the object will turn. At the same time, it might speed up, slow down, or not change speed at all. Click here to view movie.

Calculating Acceleration 2 Calculating Acceleration If an object is moving in a straight line, its acceleration can be calculated using this equation. In SI units, acceleration has units of meters per second squared (m/s2).

Positive and Negative Acceleration 2 Positive and Negative Acceleration When you speed up, your final speed always will be greater than your initial speed. So subtracting your initial speed from your final speed gives a positive number. As a result, your acceleration is positive when you are speeding up.

Positive and Negative Acceleration 2 Positive and Negative Acceleration When your final speed is less than your initial speed, your acceleration is negative. Therefore, your acceleration is negative when you slow down.

Graphing Accelerated Motion Acceleration 2 Graphing Accelerated Motion The motion of an object that is accelerating can be shown with a graph. For this type of graph, speed is plotted on the vertical axis and time on the horizontal axis.

Graphing Accelerated Motion Acceleration 2 Graphing Accelerated Motion An object that is speeding up will have a line on a speed-time graph that slopes upward. An object that is slowing down will have a line on a speed-time graph that slopes downward. A horizontal line on the speed-time graph represents an acceleration of zero or constant speed.

Section Check 2 Question 1 A change in velocity divided by the time it takes for the change to occur equals the object’s _______.

Section Check 2 Answer The answer is acceleration. Remember that, like velocity, acceleration has a direction. A car that takes a turn has changed its acceleration, even if nothing else changes.

Section Check 2 Question 2 Imagine yourself driving a car down an empty stretch of road. How many ways could you change your acceleration?

Section Check 2 Answer You could step on the gas; you could also step on the brake; you could turn the wheel, or do any combination of these.

Question 3 2 What is happening at point C in this speed-time graph? Section Check 2 Question 3 What is happening at point C in this speed-time graph?

A. the object is speeding up B. the object is slowing down Section Check 2 A. the object is speeding up B. the object is slowing down C. the object is at rest D. the object is gone

Section Check 2 Answer The answer is B. When the line falls, the object is slowing down.