Acceleration Quiz

PDF page 108: Acceleration is the change in velocity divided by a period of time during which the change occurs. The SI units of velocity are m/s

PDF page 123: • Acceleration is the rate of change of velocity and may be

PDF page 108: • Acceleration: a, measured in meters per second per second (m/s , also called meters per second squared)

PDF page 108: and the SI units for time are s, so the SI units for acceleration are m/s . Average acceleration is given by

PDF page 108: • Acceleration: a, measured in meters per second per second (m/s , also called meters per second squared)

PDF page 108: Average acceleration is distinguished from instantaneous acceleration, which is acceleration at a specific instant in time. The magnitude of acceleration is often not constant over time. For example, runners in a race accelerate at a greater rate in the first second of a race than during the following seconds. You do not need to know all the instantaneous accelerations at all times to calculate average acceleration. All you need to know is the change in velocity (i.e., the final velocity minus the initial velocity) and the change in time (i.e., the final time minus the initial time), as shown in the formula. Note that the average acceleration can be positive, negative, or zero. A negative acceleration is simply an acceleration in the negative direction. Keep in mind that although acceleration points in the same direction as the change in velocity, it is not always in the direction of the velocity itself. When an object slows down, its acceleration is opposite to the direction of its velocity. In everyday language, this is called deceleration; but in physics, it is acceleration—whose direction happens to be opposite that of the velocity. For now, let us assume that motion to the right along the x-axis is positive and motion to the left is negative.

PDF page 112: GRASP CHECK Why is acceleration a vector quantity?

PDF page 112: a. It is a vector quantity because it has magnitude as well as direction.

PDF page 108: Average acceleration is distinguished from instantaneous acceleration, which is acceleration at a specific instant in time. The magnitude of acceleration is often not constant over time. For example, runners in a race accelerate at a greater rate in the first second of a race than during the following seconds. You do not need to know all the instantaneous accelerations at all times to calculate average acceleration. All you need to know is the change in velocity (i.e., the final velocity minus the initial velocity) and the change in time (i.e., the final time minus the initial time), as shown in the formula. Note that the average acceleration can be positive, negative, or zero. A negative acceleration is simply an acceleration in the negative direction. Keep in mind that although acceleration points in the same direction as the change in velocity, it is not always in the direction of the velocity itself. When an object slows down, its acceleration is opposite to the direction of its velocity. In everyday language, this is called deceleration; but in physics, it is acceleration—whose direction happens to be opposite that of the velocity. For now, let us assume that motion to the right along the x-axis is positive and motion to the left is negative.

PDF page 108: ◦ The subscript 0 refers to an initial value; sometimes subscript i is instead used to refer to initial value.

PDF page 108: ◦ The subscript f refers to final value

PDF page 108: ◦ A bar over a symbol, such as , means average

PDF page 109: Velocity and acceleration are both vector quantities. Recall that vectors have both magnitude and direction. An object traveling at a constant velocity—therefore having no acceleration—does accelerate if it changes direction. So, turning the steering wheel of a moving car makes the car accelerate because the velocity changes direction.

PDF page 118: Earth’s surface fall with an acceleration of about 9.80 m/s . Although this value decreases slightly with increasing altitude, it

PDF page 123: acceleration due to gravity acceleration of an object that is subject only to the force of gravity; near Earth’s surface

PDF page 113: We are studying concepts related to motion: time, displacement, velocity, and especially acceleration. We are only concerned with motion in one dimension. The kinematic equations apply to conditions of constant acceleration and show how these concepts are related. Constant acceleration is acceleration that does not change over time. The first kinematic equation relates displacement d, average velocity , and time t. 3.4 The initial displacement is often 0, in which case the equation can be written as

PDF page 116: The kinematic equations are applicable when you have constant acceleration. , or 1. when d0 = 0 2. 3. , or when v0 = 0 , or 4.