PHYSICS 3200: Heat, Light and Sound

Read the Chapter on Energy by Monday, March 3.

Homework Assignment 2: Due Wednesday, March 5.

1.     A person drops a mass of 10kg.  As it is falling,

a)     What force does the earth exert on it?  (I want the magnitude and direction of the force.)

b)     What force does it exert on the earth?  (I want the magnitude and direction of the force.)

2.     I am standing on  two scales, with one foot on each one.  One reads 300N.  I actually weigh 800N.  What will the second scale read?

3.     Two cars collide.  Car A has a mass of 1500kg and car B has a mass of 2500kg.  They both exert forces on each other. 

a)     Which car will experience the larger force? 

b)     Which will experience the larger acceleration?  Why?

4.     All objects near the earth’s surface will experience the same acceleration in freefall, 9.8m/s2.  Explain why.

5.     The  box at the right experiences three forces as shown.  (The forces are in the directions of the arrows.)  The box experiences an acceleration of magnitude 0.5m/s2.

a)     What is the net force on the box? 

b)     What is the mass of the box? 

c)     What is the direction of the acceleration (Left or Right)?

6.     I am exerting a force of 100N to pull a wagon that weighs 400N along at a constant velocity.  What is the net force on the wagon?

7.     I am exerting a force of 250N to pull a wagon that weighs 600N along with a constant acceleration of 2m/s2.  What is the net force on the wagon?

8.     I throw a ball upward with a speed of 40m/s. 

a)     What will its speed be after 2s?

b)     What will its speed be after 4s?

9.     I throw a 0.4kg ball upward with a speed of 15m/s.  When it reaches the top of its trajectory, it speed will reach 0m/s and it will start back down.  At the instant its speed is zero,

a)     What is its acceleration?

b)     What is the force on the ball?

10.   Explain the concept of terminal velocity.  Use an example of a ping pong ball dropped of a tall building.  I want you to explain why it reaches a terminal velocity.

11.   Can I run around a curve with a constant speed while the net force on me is zero?  Explain!

12.   What is the difference between mass and weight?  What does each measure?