Chapter 4 - Linear Motion
When you look at a speedometer in a moving car, you can see the car's
instantaneous speed
Acceleration is defined as
the rate at which velocity itself changes
A ball is thrown straight up. At the top of its path its instantaneous speed is
0m/s
A train travels 6 meters in the first second of travel, 6 meters again during the second second of travel, and 6 meters again during the third second. It's acceleration is?
0m/s squared
a car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car's average acceleration?
6m/s^2
If you drop a feather and a coin at the same time in a vacuum tube, which will reach the bottom of the tube first?
neither they will both reach the bottom at the same time
A stone is dropped from a cliff. After it has fallen 10 m, what is the stone's velocity?
14 m/s
If a ball were equipped with a speedometer and allowed to fall freely on a planet where the acceleration due to gravity is 23m/s squared, the reading on the speedometer would increase each second by
23m/s
A bicycle travels 15 km in 30 minutes. What is its average speed?
30 km/hr (15km/30 minutes * 2)
suppose a car is moving in a straight line and steadily increases it's speed. It moves from 35km/h to 40km/h the first second and from 40km/h to 45km/h the next second. What is the car's acceleration
5km/h
Write a short paragraph explaining the difference between speed and velocity, and give examples of both.
Speed is the rate at which an object covers distance. Velocity is speed in a direction. When you get in a car and travel on a highway at 90 km/hr that is your speed. If you are traveling south, then your velocity is 90 km/h S.
One possible unit of speed is
all of the above(miles per hour; light years per century; kilometers per hour)
A car accelerates at 2m/s squared. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20m/s squared.
10 seconds
suppose you take a trip that covers 180km and takes 3 hours to make. Your average speed is
60km/h
A freely falling object starts from rest. After falling 6 seconds, it will have a speed of about
60m/s
How much time does a car with an acceleration of 5 m/s^2 take to go from 5 m/s to 40 m/s?
7 s
What is the average acceleration of a car that goes from rest to 60 km/h in 8 seconds?
7.5 km/h/s
What is the average speed of a cheetah that runs 88 m in 5 seconds?
88/5 or 17.6 m/s
Write a short paragraph explaining what acceleration is and why a car is accelerating as it rounds a corner.
Acceleration is the rate of change of velocity. Since velocity has both speed and direction, if the direction of a moving object changes, as in rounding a corner, then the object is accelerating.
Write a short paragraph on how fast things fall on Earth. Compare this to motion on the moon, where the acceleration due to gravity is about 1.6 m/s2.
The acceleration due to gravity on Earth is 10 m/s2. On the moon, it is roughly one sixth of that, or 1.6 m/s2. This means that when an object falls straight down on Earth, it gains 10 m/s of speed in each second. On the moon it gains a speed of 1.6 m/s each second.
If you drop a feather and a coin at the same time in a tube filled with air, which will reach the bottom of the tube first?
The coin
Acceleration
The rate at which velocity itself changes
suppose you are in a car that is going around a curve. The speedometer reads a constant 30mph. Which of the following is NOT true?
Your velocity is constant
suppose an object is in free fall. Each second the object falls
a larger distance than in the second before
If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by
about 10m/s
When something falls to the ground it accelerates. This acceleration is called the acceleration due to gravity and is symbolized by the letter g. What is the value of g on Earth's surface?
about 10m/s squared
In the absence of air resistance, objects fall at a constant
acceleration
Speed is
all of the above(a measure of how fast something is moving; always measured in terms of a unit of distance; distance covered per unit of time)
Acceleration is defined as the change in
velocity divided by the time interval
As an object falls freely in a vacuum, its
velocity increases
