## Physics (2017) Study Mode

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1.

Which is the incorrect formula for a body accelerating uniformly?

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A.

a = v2 - u$$\frac{2}{2}$$

B.

v2 = u2 + 2as

C.

s = $$\frac{1}{2}$$ut + at2

D.

v2 - u2= 2as

Explanation. Give a better Explanation

s = $$\frac{1}{2}$$ut + at2 is a wrong equation, it should be s = $$\frac{1}{2}$$ut + at2

2.
Which of the following is not an electromagnetic radiation?
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A.
x - ray
B.
C.
sunlight
D.
sound waves
Explanation. Give a better Explanation
Electromagnetic waves do not require any material medium, but sound waves is a mechanical wave that require a material medium

3.
Calculate the electric field intensity between two plates of potential difference 6.5V when separated by a distance of 35cm.
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A.
18.57NC$$^{-1}$$
B.
53.06N C$$^{-1}$$
C.
2.28NC$$^{-1}$$
D.
0.80NC$$^{-1}$$
Explanation. Give a better Explanation
Electric Field Intensity (E) = $$\frac{v}{d}$$

= $$\frac{\text{potential difference}}{\text{distance}}$$

= $$\frac{6.5v}{35cm}$$

= $$\frac{6.5}{35 \times 10^{- 2}}$$

= 18.57NC$$^{-1}$$

4.
Why do soldiers march disorderly while crossing a bridge?
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A.
To prevent resonance on the bridge
B.
To set the bridge into resonance
C.
To make the b ridge collapse
D.
To spread their weight evenly on the bridge
Explanation. Give a better Explanation
Soldiers march disorderly while crossing a bridge to prevent resonance because when soldiers march in orderly manner across a bridge, they generate a rhythmic oscillation of wave out. The bridge and at a certain point, would start oscillation to the same rhym as that of the marching steps. This oscillation would reach a maximum peak when the bridge can no longer sustain its own strength and hence collapses. So for this reasons, soldier are ordered to march disorderly while crossing a bridge

5.

Calculate the upthrust on an object of volume 50cm3 which is immersed in liquid of density 103kgm-3 [g = 10ms-2]

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A.

0.8N

B.

2.5N

C.

0.5N

D.

1.0N

Explanation. Give a better Explanation

Upthrust = change in weight

density = $$\frac{\text{mass}}{\text{volume}}$$

Mass of liquid displaced = Density of Liquid $$\times$$ Volume;

= 103 $$\times$$ 50 $$\times$$ 10-6m3

= 0.05kg

(Note that the volume of 50cm3 was converted to m3 by multiplying by 106) i.e 50cm3 = 50 $$\times$$ 10?6m3)

Since mass displaced = 0.05kg

Upthrust = mg = 0.05 $$\times$$ 10

= 0.5N

6.
Under what conditions are cathode rays produced in a discharge tube?
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A.
High pressure and low voltage
B.
High pressure and high voltage
C.
Low pressure and low voltage
D.
Low pressure and high volatge
Explanation. Give a better Explanation
Cathode rays are produced in a discharge tube under Low pressure and high voltage

7.
Under which of the following conditions is workdone
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A.
A man supports a heavy food above his head with his hands
B.
A boy climbs onto a table
C.
A man pushes unto a table
D.
A woman holds a pot of water
Explanation. Give a better Explanation
For work to be done, distance must be involved because
workdone = force $$\times$$ distance

8.

Calculate the specific latent heat of vaporization of steam of 1.13 x 106J, if heat energy is required to convert 15kg of it to water.

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A.

7.53 x 105 Jkg$$^{-1}$$

B.

7.53 x 10-2Jkg$$^{-1}$$

C.

7.53 x 104Jkg$$^{-1}$$

D.

7.53 x 10-3Jkg$$^{-1}$$

Explanation. Give a better Explanation

Latent Energy = mass(m) $$\times$$ specific latent heat (L)
E = mL

L = $$\frac{E}{m}$$

= $$\frac{1.13 \times 10 ^{6}}{15}$$

= 7.53 $$\times$$ 104Jkg$$^{-1}$$

9.

A cell of internal resistance 2 Ω supplies current to a 6 Ω resistor. The efficiency of the cell is

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A.

12.00%

B.

25.00%

C.

33.30%

D.

75.00%

Explanation. Give a better Explanation

Internal resistance determine the maximum current that can be supplied

Efficiency = $$\frac{r}{R}$$ $$\times$$ 100

= $$\frac{2}{6}$$ $$\times$$ 100

= 33.3%

10.
Which of the following statements is NOT correct?
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A.
Molecules of a liquid are stationary
B.
Brownian motion is an evidence of particle nature of matter
C.
Matter is made up of molecules
D.
The molecules of matter are in constant motion
Explanation. Give a better Explanation
Molecules of liquid are not stationary
Brownian motion is an evidence of particle nature of matter
matter is made up of molecules
The molecules of matter are in constant motion

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