Chapter 2: Reading Assignment 1

A car traveling 30 m/s slows down to 10 m/s in 5 seconds. The car's average acceleration is _____ m/s2.

-4

The initial velocity of a car is 30 m/s westwards. After some time, the car is traveling 45 m/s eastwards. During this interval, the car has a Δv = _____ m/s eastwards.

75

Two birds are flying in separate straight-line paths in the sky, each with a constant speed of 13 m/s. Which of the following statements must be true based solely on the previous statement? A. Both birds are traveling in the same direction. B. Both birds are traveling the same distance per second. C. Both birds have no change in their velocity. D. Both birds are accelerating. E. Both birds have the same velocities.

B. Both birds are traveling the same distance per second. C. Both birds have no change in their velocity.

The average speed of an object, s, is given by the distance of travel, d, divided by the time it takes to travel that distance, t. How would you write an equation of the time it takes to travel distance d at an average speed s? A. t=ds B. t=d/s C. t=s/d

B. t=d/s

Imagine you have taken a trip. Select all quantities about your trip that are rates. A. Distance traveled on the trip B. Trip time C. Coffees consumed per hour D. Hot dogs eaten per day E. Average acceleration during the trip F. Trip cost

C. Coffees consumed per hour (this rate is the total number of coffees consumed divided by the number of trip hours). D. Hot dogs eaten per day (this rate is the total number of hot dogs eaten divided by the number of trip days). E. Average acceleration during the trip (the average acceleration is the time rate of change of the velocity).

What does a speedometer measure? Average speed Average acceleration Instantaneous acceleration Average distance Distance from the starting location Instantaneous speed

Instantaneous speed

Match each quantity with its appropriate units (seconds, meters per second per second, meters per second, millimeters) Speed<---> ______ Distance<--->_____ Time<--->_____ Acceleration<--->_____

Speed<---> meters per second Distance<--->millimeters Time<--->seconds Acceleration<--->meters per second per second

When driving a car in a straight line, in which situations do you obtain a nonzero acceleration? When you place the car on cruise control and the speedometer stays in place When you press down farther on the gas pedal and the speedometer increases When you hold the gas pedal fixed and the speedometer stays in place When you release the gas pedal a little and the speedometer decreases

When you release the gas pedal a little and the speedometer decreases When you press down farther on the gas pedal and the speedometer increases

A student driver is having trouble maintaining constant pressure on the pedals and is driving a very "jerky" manner. Rank the following instances of acceleration from greatest to least in terms of change in velocity. Each change in velocity happens over a 1 second period of time.

from 20mph to 5mph from 10mph to 20mph from 5mph to 10mph from 39mph to 40mph

A vector must have both...

magnitude and direction

If a car goes 20 miles in 30 minutes, the average speed is _______ miles per hour.

speed=20miles/0.5hour=40miles per hour

A car traveling at 20 m/s reaches 60 m/s in 4 seconds traveling in a straight line. The car has an average acceleration of _______ m/s2.

10

The initial velocity of a car is 30 m/s westwards. After some time, the car is traveling 45 m/s westwards. During this interval, the car had a Δv = _____ m/s westwards

15

Two sprinters will race around a track. Which one will cross the finish line first? A. The one with the greatest instantaneous speed. B. The one with the greatest average speed. C. The one with the greatest instantaneous acceleration.

B. The one with the greatest average speed (The greatest average speed tells us this sprinter covered the distance to the finish line in the shortest time period).

Which units would be acceptable units of speed? Hours per kilometer Meters per mile Days per year Inches per decade Centimeters per day Meters per second per second Miles per hour

Inches per decade Centimeters per day Miles per hour

During a straight line roller coaster ride, the coaster steadily climbs up a large hill, then rolls down the hill and constantly changes speed as it quickly goes up and down smaller hills until the end of the ride when the coaster slowly comes to a complete stop.

The instantaneous acceleration will be greatest on the hills during the ride after reaching the top of the first hill.

Two sprinters will race around a track. Which one will cross the finish line first? The one with the greatest instantaneous acceleration. The one with the greatest average speed. The one with the greatest instantaneous speed.

The one with the greatest average speed.

A car traveling eastwards gains 1 m/s eastwards every second. The car is _____. Choose all that are correct. traveling with constant velocity changing its speed changing its velocity slowing down accelerating traveling with constant speed speeding up

changing its speed speeding up accelerating changing its velocity

A dropped super ball bounces off the ground and comes back up with the same speed. True or false: The ball's velocity just before bouncing was the same as immediately after it bounced.

false. because the ball's direction changed, and the velocity depends on speed and direction.

Cheetahs are the fastest mammals. Another way of phrasing this is to say that cheetahs can obtain the highest _____ speed of any mammal.

instantaneous

A ball tied to the end of a string is whirled around with a constant speed in a horizontal circle. True or False: the ball is accelerating. True false question.

true

If a car goes 90 miles in 2 hours, the average speed is _____ miles per hour.

v=90/2=45mph

The Earth travels around the sun in an almost circular orbit at an almost constant speed of 107,300 km/h (or 67,062 mi/h)! Which statement(s) are true about the Earth's motion about the sun? The Earth is not accelerating since its speed is constant. The Earth is not accelerating since we earthlings do not feel the acceleration. The Earth is accelerating since the direction of its velocity is changing. The Earth has a velocity that is always changing. The Earth cannot accelerate since it is in space. The Earth is going too fast to accelerate any more.

The Earth is accelerating since the direction of its velocity is changing. The Earth has a velocity that is always changing.

Select all the cases for which the toy car will increase its instantaneous speed. The velocity of the car is positive and the acceleration of the car is negative. The velocity of the car is positive and the acceleration of the car is positive. The velocity of the car is negative and the acceleration of the car is positive. The velocity of the car is negative and the acceleration of the car is negative.

The velocity of the car is negative and the acceleration of the car is negative. The velocity of the car is positive and the acceleration of the car is positive.

A red car has an instantaneous acceleration of 16 m/s2 westwards while a blue car has an instantaneous acceleration of 8 m/s2 westwards. Based on this information, what can be correctly stated about their motion? The red car is traveling faster than the blue car. Both cars are traveling at the same speed. The blue car is traveling faster than the red car. We do not know which car is traveling faster.

We do not know which car is traveling faster.

The difference between instantaneous speed and instantaneous velocity is that instantaneous velocity also has a ______.

direction, arrow, or bearing

A car is traveling at an average speed of 40 miles per hour. It will take the car __________ minutes to travel 10 miles.

time=10miles/40mph=15minutes

Which of the following quantities are vectors? Δt Time Velocity Acceleration Δv Speed

Δv, acceleration, velocity

In which of the following situations does the car have a nonzero acceleration? The car is on cruise control traveling around a curve. The car is parked. The car is on cruise control traveling in a straight line. The car starts from rest and speeds up to the speed limit moving in a straight line. The car is traveling at the speed limit, and then it comes to a complete stop in a straight line. The car is traveling at the speed limit and then comes to a complete stop while traveling around a curve.

The car is on cruise control traveling around a curve. The car starts from rest and speeds up to the speed limit moving in a straight line. The car is traveling at the speed limit, and then it comes to a complete stop in a straight line. The car is traveling at the speed limit and then comes to a complete stop while traveling around a curve.