Physics Chapter 2 Study Guide

Motion in One-Dimension

Frame of Reference

Frame of Reference: a system for specifying the precise location of objects in space and time.

Frame of reference Visual Concept

Displacement

Displacement is the change in position of an object.

To calculate displacement you take the final position minus the initial position.

Displacement does not always have to be only in the horizontal direction, it can also be in the vertical direction.

Example of signs for displacement

Velocity

Average velocity: the total displacement divided by the time interval during which the displacement occurred.

Velocity versus Speed

Velocity has both a magnitude (How fast it is going.) and a direction.

Graphical Interpretations

To find the velocity of the object you must calculate the slope of the position vs time graph.

For example, in the graph above the slope would be found using the points (0, 100) and (4, 1150). This gives

This means the object, a plane in this case, is travelling at 250 m/s.

The velocity vs time graph for this example is below.

If the position vs time graph is not linear, for example a parabola as in the graph below, then the slope changes constantly.

Finding the slope at different times leads to a linear graph for velocity.

Acceleration

Acceleration is the rate at which velocity changes over time; an object accelerates if its speed, direction, or both change.

Example:

Find the acceleration of an amusement park ride that falls from rest to a speed of 28 m/s in 3.0 s.

Acceleration has both a direction and magnitude.

Looking at a velocity vs time.

Point A has a positive slope, therefore it is speeding up.

Point B has zero slope, therefore it is moving at constant speed.

Point C has a negative slope, therefore it is slowing down.

Graphical Acceleration Visual Concept

Sign Conventions for acceleration

Kinematic Formulas with Constant Acceleration

Example:

A bicyclist accelerates from 5.0 m/s to 16 m/s in 8.0 s. Assuming uniform acceleration, what distance does the bicyclist travel during this time interval?

Example:

An aircraft has a landing speed of 83.9 m/s. The landing area of an aircraft carrier is 195 m long. What is the minimum uniform acceleration required for a safe landing.

Example:

An electron is accelerated uniformly from rest in an accelerator at over a distance of 95 km. Assuming constant acceleration, what is the final velocity of the electron?

Example:

A woman driving at a speed of 23 m/s sees a deer on the road ahead and applies the brakes when she is 210 m from the deer. If the deer does not move and the car stops right before it hits the deer, what is the acceleration provided by the car's brakes?

Example:

Refer to the figure to find the acceleration
of the moving object at each of the following times.

A. during the first 5.0 s of travel

B. between 5.0 s and 10.0 s

C. between 10.0 s and 15.0 s

D. between 20.0 s and 25.0 s

Example:

Refer to the figure to find the distance
traveled during the following time intervals.

A. t = 0.0 s and t = 5.0 s

B. t = 5.0 s and t = 10.0 s

C. t = 10.0 s and t = 15.0 s

D. t = 0.0 s and t = 25.0 s

Example:

A race car can be slowed with a constant
acceleration of .

A. If the car is going 55 m/s, how many meters will it travel before it stops?

B. How many meters will it take to stop a car going twice as fast?

Free Fall

Free fall is the motion of a body when only the force due to gravity is acting on the body.

Create Table in Class

Example:

A construction worker accidentally
drops a brick from a high scaffold.

a. What is the velocity of the brick after 4.0 s?

b. How far does the brick fall during this time?

Example:

A student drops a ball from a window 3.5 m above the sidewalk. How fast is it moving when it hits the sidewalk?

Example:

A tennis ball is thrown straight up
with an initial speed of 22.5 m/s. It is caught at the same distance above
the ground.

a. How high does the ball rise?

b. How long does the ball remain in the air?

Example:

You throw a ball downward from a window at a speed of 2.0 m/s. How fast will it be moving when it hits the sidewalk 2.5 m below? If the ball is thrown upward instead of downward, how fast will it be moving when it hits the sidewalk?