Physics - Online Test
Q1. A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 m each time. Assume that the potential energy lost each time she lowers the mass is dissipated. Fat supplies 3.8 J of energy per kilogram which is converted to mechanical energy with a 20 efficiency rate. How much fat will the dieter use up?
Answer : Option C
Explaination / Solution:
Work done by force applied against gravity for one lift will be
So work done for 1000 lifts = 49 x 1000 = 49000 J
efficiency = Work done / energy from fat
energy from fat used =Work done / efficiency
Energy from per kilogram fat = 3.8 J
Fat used
Q2. Submarine cables act as
Answer : Option B
Explaination / Solution:
A submarine cable consists of an inner conductor which carries power. This conductor is covered by an insulator, which acts as a dielectric. The dielectric material is covered by a metal coating called shield, which is connected to ground.
The cable acts as a cylindrical capacitor, with the conductor acting as the inner cylinder, and the metal shield as the outer cylinder which is connected to earth.
The cable acts as a cylindrical capacitor, with the conductor acting as the inner cylinder, and the metal shield as the outer cylinder which is connected to earth.
Q3. In the event of your stumbling upon a discovery, which has great academic interest but is certain to have nothing but dangerous consequences for the human society. How, if at all, will you resolve your dilemma?
Answer : Option A
Explaination / Solution:
If an invention that only cause harm to the society, it should be in safe hands only and the safe hands are only who discovered it. So it's better to keep the information upto you and your colleagues, so that all of them can work on it to make it useful for society.
Q4. A particle moves with a constant velocity parallel to the x - axis. Its angular momentum with respect to the origin
Answer : Option D
Explaination / Solution:
As angular momentum is , Now rsinθ=perpendicular distance from x axis which is constant, so angular momentum is remains constant.
Q5. Water rises to a height of 16.3 cm in a capillary of height 18 cm above the water level. If the tube is suddenly cut at a height of 12 cm
Answer : Option A
Explaination / Solution:
No Explaination.
Q6. How many atoms of helium gas fill a balloon of diameter 30.0 cm at 20.0C and 1.00 atm?
Answer : Option D
Explaination / Solution:
PV=NkTN=PVkT=1.01×105×(43×3.14×(0.15)3)1.38×10−23×293=3.53×1023
Q7. A convex crown glass lens ( = 1.5 ) has a focal length of 8 cm when placed in air. What is the focal length of the lens when it is immersed in water w
Answer : Option B
Explaination / Solution:
No Explaination.
Q8. Of the following materials, the good moderator is
Answer : Option C
Explaination / Solution:
No Explaination.
Q9. A hole is drilled in a copper sheet. The diameter of the hole is 4.24 cm at 27.0 C. What is the change in the diameter of the hole when the sheet is heated to 227 C? Coefficient of linear expansion of copper = 1.70 K–1.
Answer : Option A
Explaination / Solution:
Change in diameter
Q10. The number of significant digits in 6.320 J is
Answer : Option C
Explaination / Solution:
There are three rules on determining how many significant figures are in a number:
- Non-zero digits are always significant.
- Any zeros between two significant digits are significant.
- A final zero or trailing zeros in the decimal portion ONLY are significant.
So keeping these rules in mind, there are 4 significant digit.
