NECO Physics Past Questions & Answers - Page 48

236.

In which of the following are the substances arranged in descending order of their thermal conductivities?

A.

aluminum, copper, iron

B.

aluminum, iron, copper

C.

copper, aluminum, iron

D.

copper, iron. aluminum

E.

iron, copper, aluminum

Correct answer is C

metals                    thermal conductivity( W/mk)

IRON                          65.7

COPPER                   377

ALUMINIUM              218

THERMAL CONDUCTIVITIES OF Al, Fe, and Cu at 100degree Celsius

237.

Which statement is NOT correct about Rutherford’s model of the atom?

A.

The diameter of the nucleus is of the order of 10-15m

B.

The mass of an atom is concentrated in the nucleus

C.

The model is applicable to atoms with one electron in the outer shell

D.

The nucleus of an atom is positively charged

E.

The nucleus is surrounded by an electron cloud.

Correct answer is C

No explanation has been provided for this answer.

238.

A brass cube of side 10cm is heated through 30°C. If the linear expansivity of brass is 2.0 × I0\(^{-5}\) K-1 , what is the increase in its volume?

A.

0.06 cm3

B.

0.18cm3

C.

0.60cm3

D.

1.20cm3

E.

1.80cm3

Correct answer is E

cubic expansivity and γ = 3α. → 3 * 2.0 × I0\(^{-5}\)

cubic expansivity = 6.0 × I0\(^{-5}\) , Ø = 30°C,

Volume(v\(_1\)) = L\(^3\) = 10\(^3\) → 1000

V\(_2\) = V\(_1\)(1 + γθ)

→ V\(_2\) = 1000[1 +  6.0 × I0\(^{-5}\) * 30]

= 1000[1 + 0.0018]

= 1000 * 1.0018 → 1,001.8

 increase in volume = 1,001.8 - 1000 

→ 1.8cm\(^3\)

239.

A body of mass 4 kg is accelerated from rest by a steady force of 9N. What is its speed when it has travelled a distance of 8m?

A.

6 ms-1

B.

18 ms-1

C.

32 ms-1

D.

36 ms-1

E.

48 ms-1

Correct answer is A

No explanation has been provided for this answer.

240.

What is the escape velocity of a satellite launched from the earth’s surface? (Take g as 10ms-2 and the radius of the earth as 6.4 × 106m)

A.

7.80 × 10kms-1

B.

11.2 × 10kms-1

C.

3.56 × 107ms-1

D.

6.00 × 107ms-1

E.

1.20 × 108ms-1

Correct answer is B

 The escape speed from Earth's surface is about 11.186 km/s