Quiz 1 Key

1.  The measured length of a cylindrical laser beam is 12.1 meters, its measured diameter is 0.00121 meters, and its measured intensity is 1.21 ´ 10⁵ W/m². Which of these measurements is the most precise?  

A.  length
B.  diameter
C.  intensity
D.  All three are equally precise.

2.  Vectors A and B have the same non-zero magnitude. The magnitude of A + B is equal to the magnitude of A - B . What is the angle between  A and B ? 

A. 30 degrees
B. 45 degrees
C. 60 degrees
D. 90 degrees

3. How many significant figures are in the number 0.00640? 

A. 1
B. 2
C. 3
D. 4
E. 5

4. A vector  A with magnitude 25.0 m points along the positive y direction. If it is rotated by 50.0 degrees counterclockwise, what are the components of the vector? 

A. A_x = 25.0 cos 50.0° and A_y = 25.0 sin 50.0°
B. A_x = 25.0 cos 140° and A_y = 25.0 sin 140°
C. A_x = 25.0 sin 140° and A_y = 25.0 cos 140°
D. A_x = 25.0 tan 50.0° and A_y = 25.0 sin 50.0°
E. All solutions above are wrong.

5. Assume that the mass of any cell in the human body is 5 ´ 10^-15 kg. If Alice has a mass of 50 kg how many cells are there in her body? 

A. 10¹⁷ cells
B. 10¹⁶ cells
C. 10¹⁵ cells
D. 10¹⁴ cells
E. 10¹³ cells

6.  The answer with the correct number of significant figures to the following calculation: 1.345 ´ 6.72 + 4.51 is  

A.  13.5484.
B.  13.548.
C.  13.55.
D.  13.6.
E.  14

7.  If vector  and vector  , where  and  are the units vectors along the x and the y directions respectively, calculate the magnitude of vector  .  

A.  10.3
B.  17.4
C.  -6.7
D.  26
E.  -12.3

8.  The fraction of a cubic kilometer in a cubic millimeter is  

A.  10^-18.
B.  10^-12.
C.  10^-9.
D.  10^-6.

9. A cube with a volume of V consists of 6 faces each with an area of A. If the area of each face is increased by a factor of 64, by what factor does the volume increase? 

A. 8
B. 64
C. 384
D. 512
E. 4096

10.  Vector A points along the y axis with length 5.0, vector B makes an angle of 55° with respect to the x-axis and has a length of 7.0. What is the length of vector A - B?

     
A.  4.1
B.  12.
C.  2.0
D.  35.
E.  9.9

General Physics Quiz 1

https://www.facebook.com/GeneralPhysics

https://plus.google.com/communities/107560119663318352211

https://twitter.com/GeneralPhysics

http://generalphys.blogspot.com/

Quiz, Chapter 17, 18

Student Last Name__________________________First Name_____________________9/24/2014

1. Two point charges are placed on the x axis as follows:
Charge q1 = 1 mC is located at x =  1 m, and charge q2 = 2 mC is at x = -3 m.
What are the magnitude and direction of the net force exerted by these two charges on a third charge q3 = -1  mC placed on the origin?

2. Charge q1 = 3 mC is located on the x axis at x =  -1 m, and charge q2 = 1 mC is located on the y axis at y = -0.5 m.
What are the magnitude, the x and y components, and the angle with the x direction of the net force exerted by these two charges on a third charge q3 =  1  mC placed on the origin?

3. A point charge of -4 nC is at the origin, and a second point charge of -1 nC is on the x axis at x = 6 m. Find the magnitude and direction of the  electric field at each of the following points on the x axis:
(a) x = 4 m,
(b) x = 12 m.

4. A point charge Q = 1 mC is held fixed at the origin. A second point charge q = 2 mC with mass of 1 kg is placed on the x axis , 1 m from the origin.
(a) What is  the electric potential energy U of the pair of charges?
(b) The second point charge is released from rest. What is its kinetic energy when its distance from  the origin is
(i) 2m;
(ii) 20 m;
(iii) 200 m.  

5. A 1 mF capacitor is connected to a power supply that keeps a constant potential difference of 1 V across the plates. A piece of material having a dielectric constant of 4 is placed between the plates, completely filling the space between them.
How mach energy is stored in the capacitor before and after the dielectric is inserted?