10/3 MS Physics class and homework due 10/10

Hi folks,

Today we moved our conversation of motion forward by discussing the concept of acceleration.  We did a lab where we found how the speed of a rubber band car changed over time.  

For homework this week please answer the following questions.  (I've included answers so that you can check yourself when you are done.  Be sure to study this homework, your past homework and your last quiz.  There will be a quiz next week so be ready!)

1.  What is the definition of velocity?

2.  How is velocity different than speed?

3.  What is the definition of acceleration?

4.  What does velocity have to do with acceleration?

5.  What three things can a driver do to accelerate a car?

6.  A kicker kicks a ball high into the air and when it comes down it stops dead in a sand pit.  

a.  When is the ball accelerating?

b.  When is the ball accelerating the most?

7.  If a bicycle is coming to a stop is it accelerating?

8.  When we shot our Nerf guns last week, when did the dart accelerate the most?

9.  Give me an example of something accelerating.

10.  Can something be going 405 mph and not be accelerating?

11.   Take a look at the graph and data table below.  It's the data you took in class today.  Please answer the following questions using the data and the graph.

a.  Which car reached the highest speed?  What was the speed?

b.  Which car had the greatest acceleration (the most speed change in the shortest amount of time)?  (Careful on this, the graph is a bit different than it was in class.)

c.  When did the car represented by the blue graph slow down?  How do you know?

 12.  What are two possible causes of error in this lab?  In other words, where are two areas that mistakes could have happened to cause the data to be incorrect.

ANSWERS (Please only use to check yourself!!!!!!  Your answer do not need to be word for word the same as mine but they do need to have the same meaning. )

1.  Velocity is speed AND direction.

2.  Speed is just distance and time but velocity is the amount of time it takes to travel a distance in a certain direction.

3.  Acceleration is speeding up, slowing down or changing direction.

4.  Acceleration is what causes velocity to change.  (Careful, acceleration and velocity are two different things.)

5.  Hit the brakes, step on the gas and turn the steering wheel.  (Hopefully not at the same time however!)

6.  a. The ball is accelerating the entire time.  As it goes up it's slowing down, as it's coming down, it's speeding upt.

b.   The ball changes speed the fastest when it hits the ground.

7.  Yup, slowing down is accelerating.

8.  When it was shot from the gun.  It went from 0 mph to 30 mph in a VERY short time.  

9.  Any example of something changing speed is good here.

10.  Yup, it can be going any speed but if it's not changing speed it is not accelerating.

11.  a. Group #1's car reached a speed of 65 ft/s

b.  Group #3's car.  It went from 0 - 48 in the first second!

c.  It slowed down between the 2nd and 3rd second.  I can see that because the graph goes downward.  Also because the numbers on the data table also show that.

12. There are many answers to this but some could be, errors in timing; not marking the location of the car at each second well;  not measuring well;  the timer and the car start at different time.