## Thursday, 20 August 2015

### UNITS AND MEASUREMENT MCQ

1. The SI standard of time is based on:
A. the daily rotation of the earth
B. the frequency of light emitted by Kr86
C. the yearly revolution of the earth about the sun
D. a precision pendulum clock
E. none of these
Ans: E
2. A nanosecond is:
A. 109 s
B. 10−9 s
C. 10−10 s
D. 10−10 s
E. 10−12
Ans: B
3. The SI standard of length is based on:
A. the distance from the north pole to the equator along a meridian passing through Paris
B. wavelength of light emitted by Hg198
C. wavelength of light emitted by Kr86
D. a precision meter stick in Paris
E. the speed of light
Ans: E
4. In 1866, the U. S. Congress defined the U. S. yard as exactly 3600/3937 international meter.
This was done primarily because:
A. length can be measured more accurately in meters than in yards
B. the meter is more stable than the yard
C. this definition relates the common U. S. length units to a more widely used system
D. there are more wavelengths in a yard than in a meter
E. the members of this Congress were exceptionally intelligent
Ans: C
5. Which of the following is closest to a yard in length?
A. 0.01m
B. 0.1m
C. 1m
D. 100m
E. 1000m
Ans: C

6. There is no SI base unit for area because:
A. an area has no thickness; hence no physical standard can be built
B. we live in a three (not a two) dimensional world
C. it is impossible to express square feet in terms of meters
D. area can be expressed in terms of square meters
E. area is not an important physical quantity
Ans: D

7. The SI base unit for mass is:
A. gram
B. pound
C. kilogram
D. ounce
E. kilopound
Ans: C
8. A gram is:
A. 10−6 kg
B. 10−3 kg
C. 1 kg
D. 103 kg
E. 106 kg
Ans: B
9. A sphere with a radius of 1.7 cm has a volume of:
A. 2.1 × 10−5 m3
B. 9.1 × 10−4 m3
C. 3.6 × 10−3 m3
D. 0.11 m3
E. 21 m3
Ans: A
10. 24. A square with an edge of exactly 1 cm has an area of:
A. 10−6 m2
B. 10−4 m2
C. 102 m2
D. 104 m2
E. 106 m2
Ans: B

## Wednesday, 12 August 2015

### Velocity Problems and Physical dimension problems

1 .Bicyclist A starts with initial displacement zero and moves with velocity 3m/s.At the same
time:   bicyclist B starts from a point with displacement 200m and moves with velocity      -2m/s  When does A meet B and where are they when this happens?
2.The initial displacement of a body moving with a constant velocity 5m/s is -10m .When does  the body  reach the point with displacement 10m? What distance does the body cover in this  time?
3. A mass has an initial velocity of 10m/s .It moves with acceleration -2.00 ms-2 .When will    it have zero velocity?
4.Object A starts from the origin with velocity 3m/s and object B starts from the same place with velocity 5m/s , 6 seconds later. When will B catchup with A?
5.An object moving in a straight line has a displacement-time graph as shown in figure
a     Find the average speed for the trip. Find the average velocity for the trip.6. What do you mean by Physical dimension and What are its Uses?

6.Draw roughly velocity-Time graph for an an object moving with constant velocity.

7.Draw roughly distance –time for an object which is at rest.

8.E, m, L, G denote energy, mass, angular momentum & gravitation constant respectively. Then what willbe dimensions of  EL2 /m5G2?

9.If the speed of light (C), acceleration due to gravity(g) and pressure (P) are taken as fundamental units, then find dimensions of gravitational constant (G)

10.what are the different types of Errors and how it could be minimised.

11.Derive equations of motion by using calculus

12.A mass starts out from O with velocity 10m/s and continues moving at this velocity for 5s. The velocity is then abruptly reversed to -5m/s and the object moves at this velocity for 10 s. For this motion find:
a) the change in displacement
b) the total distance travelled
c) the average speed
d)the average velocity

### Speed displacement Problems

1.Define acceleration and State its SI unit.
2.What do you mean by Instantaneous velocity?
3.The Density of water in CGS system is 1 g/cc ,Write its unit in Kg/m3
4.What is a light year?
5.Differeiate between Absolute error and elative error?
6. A mass initially at O, first moves 5m to the right and then 12m to the left .What is the total distance covered by the mass and what is its change in displacement?
7.A car 4.0m long is moving to the left. It is observed that it takes 0.10 s for the car to pass a given point on the road. What is the speed and velocity of the car at this instant of time?
8. An object has a displacement of -5m.It moves a distance to the right equal to 15m and then a distance of 10m to the left. What is the total distance travelled and final displacement of the object? What is the change in displacement of the object?
9.A car of length 4.2 m travelling in a straight line takes 0.56 s to go past a mark on the road. What is the speed of the car?

10.A car starts out from O in a straight line and moves a distance of 20 Km towards the right, and then returns to its starting position 1 hr later.what is the average speed and the average velocity of the trip?

## Monday, 3 August 2015

### VECTOR ADDITION UPSTREAM AND DOWNSTREAM PROBLEMS

1. Add the following vectors and determine the resultant.
3.0 m/s, 45 deg and 5.0 m/s, 135 deg
2. Add the following vectors and determine the resultant.
5.0 m/s, 45 deg and 2.0 m/s, 180 deg

3. Add the following vectors and determine the resultant.
6.0 m/s, 225 deg and 2.0 m/s, 90 deg

4. Add the following vectors and determine the resultant.
4.0 m/s, 135 deg and 4.0 m/s, 315 deg
5. A plane can travel with a speed of 80 mi/hr with respect to the air. Determine the resultant velocity of the plane (magnitude only) if it encounters a
b. 10 mi/hr tailwind.
c. 10 mi/hr crosswind.
d. 60 mi/hr crosswind.
6. A motorboat traveling 5 m/s, East encounters a current traveling 2.5 m/s, North.
a. What is the resultant velocity of the motor boat?
b. If the width of the river is 80 meters wide, then how much time does it take the boat to travel shore to shore?
c. What distance downstream does the boat reach the opposite shore?
7. A motorboat traveling 5 m/s, East encounters a current traveling 2.5 m/s, South.
a. What is the resultant velocity of the motor boat?
b. If the width of the river is 80 meters wide, then how much time does it take the boat to travel shore to shore?
c. What distance downstream does the boat reach the opposite shore?
8. A motorboat traveling 6 m/s, East encounters a current traveling 3.8 m/s, South.
a. What is the resultant velocity of the motor boat?
b. If the width of the river is 120 meters wide, then how much time does it take the boat to travel shore to shore?
c. What distance downstream does the boat reach the opposite shore? 5. If the current velocity in question #4 were increased to 5 m/s, then
a. how much time would be required to cross the same 120-m wide river?

b. what distance downstream would the boat travel during this time?

### ELECTRICITY RESISTANCE AND RESISTIVITY PROBLEMS

1.A wire of resistance R is bent in form of a closed circle, what is the resistance across a diameter of the circle?
2. Two wires of equal cross sectional area , one of copper and other of
Manganin have same resistance. Which one will be longer?
3. A Rectangular block of iron has dimensions L X L X b. What is the
resistance ofthe block measured between the two square ends ? Given ρ=
resistivity.
4. Three equal resistances are connected in series then in parallel. What will
be the ratio of their Resistances?
5. Two cubes A and B are of the same material. The side of B is thrice as that
of A.Find the ratio RA/RB.
6. A nichrome wire of resistivity 100X10-6ohm- m and copper wire of
resistivity1.62X10-8 ohm-m of same length and same area of cross section
are connected in series , current is passed through them, why does the

nichrome wire gets heated first?

7. A parallel combination of three resistances take a current of 7.5 A from a 30 V battery. If two
of    the resistance values are 10 Ω and 12 Ω, find the third.

8. A string of fifty 15 ohm Christmas tree lights are connected in series. One burns out, they all burn out. Calculate the total resistance.

9. A 10 ohm, 20 ohm, and 100 ohm resistors are connected in parallel. Calculate the total
resistance.