Question

1. Two identical objects of the same mass come into thermal contact with each other. If object A is at   20^o C  and the object B is at 90^o C  , then the equilibrium temperature will be

   	a.	20o C
   	b.	110o C
   	c.	90o C
   	d.	55o C

2. If a flat metal plate with a circular hole cut through it is heated,

   	a.	the hole gets larger.
   	b.	the hole may get larger or smaller, depending on how much the plate is heated.
   	c.	the hole may get larger or smaller, depending on the material of the plate.
   	d.	the hole gets smaller.
   	e.	the hole stays exactly the same size.

3. QUESTION 31

4. When a source of sound approaches, measurements will show an increase in the sound's  
   1) speed,  
   2) frequency,  
   3) wavelength,  
   4) all of these,  
   5) none of these,
   
   and when a source of sound recedes, measurements will show an increase in the sound's  
   6) speed.  
   7) frequency.  
   8) wavelength.  
   9) all of these.  
   10) none of these.

   Note: Your answer must have the first choice, comma, then the second choice. For example, input 3, 7 for choices 3 and 7.

5. Consider a car that starts at rest and accelerates at 2 m/s² for 3 seconds. At that time, t = 3 s, how fast is it going?

   	a.	6 m/s
   	b.	3 m/s
   	c.	9 m/s
   	d.	12 m/s

6. Light refracts or reflects for a mirror, and light refracts or reflects for a lens

   	a.	refracts, refracts
   	b.	reflects, reflects
   	c.	refracts, reflects
   	d.	reflects, refracts

7. How did you determine the location of a virtual image with a ray diagram for a mirror?

   	a.	Retrace the reflected lines onto the right side of the mirror.
   	b.	Retrace the incident lines onto the right side of the mirror.
   	c.	Determine the location of the intersection point on the left side of the mirror.

8. How did you determine the location of a virtual image with a ray diagram for a mirror?

   	a.	Retrace the reflected lines onto the right side of the mirror.
   	b.	Retrace the incident lines onto the right side of the mirror.
   	c.	Determine the location of the intersection point on the left side of the mirror.

Answer 1

For identical objects of same mass equilibrium temperature is average of temperature of two objects. Hence 55 deg C

Hole gets larger. It behaves exactly the way material would have behaved, if there were no hole.

31) 2 ,8

With source approaching, frequency increases and wavelength decreases. With source receding, frequency decreases and wavelength increases.

-. Vfinal = Vinitia + at

= 0. + 2m/s^2 * 3 sec = 6 m/s

Option a

-. Reflects from mirror and refracts from lens

Option d

-. Virtual image is located by retracing, reflected rays to the right or behind the mirror.

Option a