Concept Physic Unit 1 Chapter 2 - Linear Motion

Suppose a car is moving in a straight line and steadily increases its speed. It moves from 30 m/s to 40 m/s the first second and from 40 m/s to 50 m/s the next second. What is the car's acceleration?

10m/s^2

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 , the reading on the speedometer would increase each second by _________________.

23 m/s.

Suppose you take a trip that covers 180 km and takes 6 hours to make. Your average speed is _________.

30 km/h.

A car starts from rest and after 6 seconds it is moving at 42 m/s. What is the car's average acceleration?

7m/s^2

FORMULA INSTANTANEOUS SPEED

Acceleration per elapse time

instantaneous speed

speed at any instant in time

rate

how fast something happens, or how much something changes over a period of time (amount of change divided by time)

speed

how fast something is moving (distance divided by time)

Changing velocity

if either the speed or the direction (or both) is changing, then the velocity is changing

When you look at the speedometer in a moving car, you can see the car's.

instantaneous speed.

Motion

is describe relative to something, its occurs all around us.

Does the speedometer of a car read instantaneous speed or average speed?

it displays instantaneous speed.

kilometer

a metric unit of measurement equal to 1,000 meters (approximately 0.62 miles).

The speedometer of a car moving northward reads 60km/h. It passes another car that travels. Southward at 60 km/h. Do both cars have the same speed? Do they have the same velocity?

Both cars have the same speed, but they have opposite velocities because they are moving in opposite directions.

What are some devices used to measure time?

CLOCK Metronome Sundial Hourglass

What do we mean when we say that motion is relative? what is everyday motion usually relative to?

Motion is the movement of one thing compared to another. The Sun and Stars

The speedometer in every car also has an odometer that records the distance traveled.

a) If the odometer read zero at the beginning of a trip and 35 km a half hour later, what is the average speed. average speed= 35km divided by 0.5h = 70 km/h

A ball is thrown straight up. At the top of its path its instantaneous speed is

a. 0 m/s.

1. Speed is __________.

a. a measure of how fast something is moving. b. always measured in terms of a unit of distance divided by a unit of time. c. the distance covered per unit time. d. all of the above

relative

depends on the point of view or frame of reference

In physics, velocity is defined as

displacement divided by time where displacement is defined as the difference between your final and initial positions

What is the difference between instantaneous speed and average speed?

instantaneous speed is the speed at any given instant,whereas average speed is the quotient(division) of total distance and total time.

velocity

speed combined with direction of motion

hang time

the amount of time a jumper is airborne

acceleration

the rate at which velocity is changing, which can be a magnitude, direction, or both

A ball is thrown upwards and caught when it comes back down. In the absence of air resistance, the speed of the ball when caught would be

the same as the speed it had when thrown upwards.

elapsed time

the time that has passed since the beginning of an event

How far will a freely falling object have fallen from a position of rest when its instantaneous speed is 10m/s/

5 m (its average speeed would be 5 m/s).

For a freely falling object dropped from rest, what is the instantaneous speed at the end of the fifth second of fall? The sixth second?

50 m/s; 60 m/s (when g= 10 m/ss).

free fall

motion under the influence of the gravitational force only

average speed

path distance divided by time interval

How far will a freely falling object fall from rest in five seconds? Six seconds?

125 m ; 180 m.

A car accelerates at 10 . Assuming the car starts from rest, how much time does it need to accelerate to a speed of 20 m/s?

2 seconds

Approximate Speed in different Unit

20 km/h = 12mile = 6m/s 40 km/h = 25mile = 11m/s 60 km/h = 37mile = 17m/s

16. A freely falling object starts from rest. After falling for 3 seconds, it will have a speed of about

30 m/s.

17. If a projectile is fired straight up at a speed of 20 m/s, the total time to return to its starting point is about

4 seconds.

table free fall speed of object Dropped from Rest.

ELAPSE TIME = 1 INSTANTANEOUS SPEED =10

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?

Neither—they will both reach the bottom at the same time.

if the speedometer of a car reads a constant speed of 40km/h can you say that the car has a constant velocity?

No. If the car is changing direction, the velocity is changing even though the speed remains constant.

What are some devices used to measure distance? __

Ruler Tape Odometer

What are some ways you know of to measure speed?

SPEEDOMETER Tape measure

mile

any of various units of distance, such as the statute mile of 5,280 feet (1.609 km). I

Formula average speed

average speed = Total distance covered divided by time interval

Toss a ball upward. What is the change in speed each second on the way up? On the way down?

9.8 m/s (or approximately 10 m/s) at all times.

For a freely falling object dropped from rest, what is the acceleration at the end of the fifth second of fall? The sixth second? At the end of any elapsed time t?

9.8 m/ss (or approximately 10 m/ss) at all times.

What would the speedometer reading on the falling rocks 4.5 second after it drops from rest? How about 8 seconds after it is dropped 15 second.

The speedometer reading would be 45m/s 80m/s and 150m/s respectively. You can reason this from use the equation v=gt where g is replaced by 10 m/s.

suppose a car moving in a straight line steadily increases its speed each second, first from 35 to 40km/h, then from 40 to 45km/h then from 45 to 50 km/h. What is it aceleration

We see that the speed increases each 1-s interval. The acceleration is therefore 5km/h-s during each interval

Suppose you are in a car that is going around a curve. The speedometer reads a constant 30 miles per hour. 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.

A ball is thrown straight up. At the top of its path its acceleration is

about 20m/s .

In the absence of air resistance, objects fall at constant

acceleration.

Acceleration is defined as the CHANGE in ___________.

velocity divided by the time interval

what is the difference between speed and velocity?

velocity is a speed given in an certain direction.

Constant velocity

when an object travels the same distance every second, then the object is said to be moving constant velocity