Problems for Chapter 2.

1. Benjamin watches a thunderstorm from his apartment window. He sees the flash of lightning and then starts counting until he hears the thunder 10 seconds later. Assuming that the speed of sound is 340 m/s, how far away is the storm?

2. Peter is driving his Porsche at 30 m/s when a ball rolls out into the street in front of him. He slams on the brakes and comes to a stop in 4.5 seconds. What was the acceleration of Peter’s car?

3. Sharon is driving on the freeway at 20 m/s when she decides to speed up and pass a slow moving truck using the left lane. If she can accelerate at 5 m/s², how long will it take her to reach 32 m/s? How much distance will she cover in this time?

4. A baby blue jay sits in a tall tree awaiting the arrival of its dinner. As the mother lands on the nest, she drops a worm toward the chick but misses. The worm then drops from the nest to the ground in 1.50 seconds. How high up is the nest?

5. When we did the dollar bill game in class we had a hard time doing it. Do the following calculations to show why. Human reaction time is rarely less than 0.20 seconds. A dollar bill is .155m long and should be started right at finger level. How long does it take to fall past the fingers?

6. Mr. Khoury challenges Mr. Little to a 100m race on the football field. The loser must grade the other’s labs for a month. Mr. Khoury runs the race in 13.45 seconds. Mr. Little runs the first 25.0m with an average speed of 13.5 m/s, the next 50m with an average speed of 12.9 m/s and the last 25m with an average speed of 13.8 m/s. So who is going to be spending late nights at St. Mary’s? Explain.

7. A Christmas tree ball will break if dropped on a hardwood floor with a speed of 2m/s or more. Holly is decorating her tree when her cat taps a ball causing it to fall 15cm from a tree branch to the floor. Does the ball break?

8. Francis is practicing juggling. If she tosses a ball upwards at a speed of 10 m/s how long will it take for the ball to return to the same height from which she threw it? How high up will it go?

9. The Empire State Building is 321 m tall. If someone dropped a penny from the top and air resistance is ignored, how long will it take to get to the ground? How fast would it be going when it hit the ground? Why doesn’t the penny really go this fast?

10. Monica is walking to the hairdresser’s at a velocity of 1.3 m/s when she glances at her watch and realizes that she is running late. She gradually quickens her pace by accelerating at 0.090m/s2. If she accelerates for 10 seconds how fast will she be going? At this final speed do you think she is walking, jogging or running fast? Try it and find out!

11. For many years, the posted highway limit was 88.5 km/hr. (55mph) but then many stretches of highway have changed the limit to 104.6 km/hr (65 mph). In Maine, the highway between Portland and Bangor made such a change. If these cities are 215 km apart, how much time would a person save driving the limit now, compared to the time it took at the old limit?

12. The Tambora volcano on the island of Sumbawa, Indonesia has been known to throw ash into the air with a speed of 625 m/s during an eruption. a) How high could the volcanic plume have risen? b) How long would it take for ash to reach this peak? c) On Venus, where the acceleration due to gravity is slightly less than on Earth, would the plume rise higher or not as high as on Earth?