# Physics exercises | Physics homework help

Exercises:

2. How many individual atoms are in a water molecule?

3. When a container of gas is heated, what happens to the average speed of its molecules?

4. The average speed of a perfume – vapor molecule at room temperature may be about 300 m/s, but you ‘ll find the speed at which the scent travel across the room in much less. Why?

5. A cat scrolls across your backyard. An hour later, a dog with his nose to the ground follows the trail of the cat. Explain this occurrence from a molecular point of view?

10. Your friend says that what makes one element disctinct from another is the number of electrons about the atomic nucleus. Do you agree wholeheartedly, partially, or not at all? Explain.

12. Why don’t equal masses of golf balls and Ping-Pong balls contain the same number of balls?

15. How many atoms are in a molecule of ethanol, C2H6O?

17. A particular atom contains 29 electrons, 34 neutrons, and 29 protons. What is the identity of this element and its atomic number?

23. You could swallow a capsule of germanium without ill effects. But, if a proton were added to each of the germanium nuclei, you would not want to swallow the capsule. Why? (Consult the periodic table)

31. In what sense can you truthfully say that you are a part of every person in history? In what sense can you say that you will tangibly contribute to every person on Earth who will follow?

One step calculation:

**Speed = distance**

** Time**

1.Calculate your walking speed when you step 1 meter in 0.5 second.

**Average = total distance covered**

** Time interval**

3.Calcualte your average speed if you run 50 meters in 10 seconds.

5.Calcualate the average speed of a cheetah that runs 140 meters in 5 seconds.

**Distance = average speed X time**

** **

7. Calculate the distance (in km) that Larry runs if he maintains an average speed of

8 km/h for 1 hour.

9. Calculate the distance you will travel if you maintain an average speed of 10 km/h

for one-half hour.

**Acceleration = change of velocity**

** Time interval**

11. Calculate the acceleration of a bus that goes from 10 km/h to a speed of 50 km/h in 10 seconds.

13. On a distant planet, a freely falling object gains speed at a steady rate of 20 m/s during each second of fall. Calculate its acceleration.

**Instantaneous speed = acceleration x time**

15. Calculate the speed (in m/s)of a skateboarder who accelerates from rest for 3 seconds down a ramp at an acceleration of 5 m/s square.

** **

**Velocity acquired in free fall from rest: v=gt (where g=10 m/s square)**

17. An object is dropped from rest and falls freely. After 7 seconds, calculate its instantaneous speed.

**Distance fallen in free fall, from rest: d=1/2 gt square**

19. A coconut drops from a tree and hits the ground in 1.5 seconds. Calculate how far it falls.