Physics Test

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Physics Test - 5

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Weekly Quiz Competition

Question 1
1 / -0

When an electron-positron pair annihilates, how much energy is released?

A
0.8 x 10-13

B
1.6 x 10-13J

C
3.2 x 10^-13 J

D
4.6 x 10-13J

Solution
Question 2
1 / -0

Directions: In the following question, a statement of Assertion is given, followed by a corresponding statement of Reason. Mark the correct answer as:
(a) If both Assertion and Reason are true and the Reason is the correct explanation of the Assertion.
(b) If both Assertion and Reason are true, but the Reason is not the correct explanation of the Assertion.
(c) If Assertion is true, but Reason is false.
(d) If both Assertion and Reason are false.
Assertion : Neutrons penetrate a matter more readily as compared to protons.
Reason : Neutrons are slightly more massive than protons.

A
A

B
B

C
C

D
D

Solution

Here assertion given is correct. The reason given for the assertion is correct but it is not the reason for the assertion.
Question 3
1 / -0

If M0is the mass of an oxygen isotope8O17, and Mpand Mnare the masses of a proton and a neutron, respectively, then what is the nuclear binding energy of the isotope

A
(M0- 8M)c2

B
(8Mp+ 9Mn- Mo)c2

C
Moc2

D
(Mo- 17Mn)c2

Solution

Here, Z = 8 and A = 17, therefore,
B.E. = (8M_p+ (17 - 8)M_n- M_o)c²
= (8M_p+ 9M_n- M_o)c²
Question 4
1 / -0

A shell at rest, at the origin explodes into three fragments of masses 1 kg, 2 kg and m kg. The pieces weighing 1 kg and 2 kg fly off with a speed of 5 ms–1along x– axis and 6 ms–1along y– axis respectively. If the 'm' kg piece flies off with a speed of 6.5 ms–1, what must be the total mass of the shell?

A
4 kg

B
5 kg

C
3.5 kg

D
4.5 kg

Solution
Question 5
1 / -0

A nucleus decays by+emission, followed by-emission. If the atomic and mass numbers of the parent nucleus are Z and A, respectively, then the corresponding numbers for the daughter nucleus are

A
Z - 1 and A - 1

B
Z + 1 and A

C
Z - 1 and A

D
Z + 1 and A - 1

Solution

For the positron emission, the mass number decreases by 1 and atomic number remains same. Hence, the corresponding numbers for the daughter nucleus are Z - 1 and A.
Question 6
1 / -0

A heater wire consumes power `P` when connected to a 220V source. If the wire is cut into four equal pieces, which are now connected in parallel, find the power consumed by the combination, if connected to the same power supply.

A
4P

B
P/4

C
16P

D
P/16

Solution
Question 7
1 / -0

Two electric bulbs rated P1watt V volt, and P2watt V volt are connected in parallel, and applied across V volt. The total power will be

A
(P1 + P2) watt

B

C

D

Solution
Question 8
1 / -0

If power dissipated by 5Ω resistor is 20 W, then find the power dissipated by 4Ω resistor.

A
10 W

B
20 W

C
4 W

D
15 W

Solution
Question 9
1 / -0

The thermo emf produced in a thermocouple is 3μV/oC. If the temperature of the cold junction is 20oC and the thermo emf is 0.3 mV, the temperature of the hot junction is

A
80^oC

B
100^oC

C
120^oC

D
140^oC

Solution
Question 10
1 / -0

Consider the following two statements A and B and identify the correct answer.

A:Constantan-Copper thermo-couple is generally used to measure temperature upto 1600oC.

B:In an iron-copper thermocouple, current flows from iron to copper through cold junction.

A
Both A and B are true.

B
Both A and B are false.

C
A is true but B is false.

D
A is false but B is true.

Solution

Both A and B are true. In an iron-copper thermocouple, current flows from iron to copper since iron comes first in see back list.
Question 11
1 / -0

A triangle ABC forces acting along lA, lB and lC, respectively, in equilibrium, where l is the incentre of ABC. Then, is

A
cos A : cos B : cos C

B

C

D
sin A : sin B : sin C

Solution
Question 12
1 / -0

A
3 : 1 : 1

B
2 : 3 : 2

C
1 : 2 : 3

D
2 : 3 : 1

Solution
Question 13
1 / -0

If the forces of magnitude 12 Kg wt, 5 Kg wt and 13 Kg wt acting at a point are in equilibrium, then the angle between the two forces is

A
30⁰

B
900

C
600

D
450

Solution

Since (13)2= (12)²+ (5)²
So two of them are inclined at 90 to each other.
Question 14
1 / -0

Two men carry a weight of 240 kg between them by means of two ropes fixed to the weight. One rope is inclined at 60× to the vertical and the other at 30×. The tensions in the ropes are

A
120 kg, 120 kg

B
120√3 kg, 120 kg

C
120√3 kg, 120√3 kg

D
None of these

Solution
Question 15
1 / -0

The resultant of P and Q is R. If P is reversed, Q remains the same, the new resultant S is at right angle to R. The value of P / Q is

A
1

B
2

C
1/2

D
none of these

Solution