Railway Science (Physics-Units and Measurements) (Part-II)

Total Questions: 31

21. Unit of power is called a: [RRB ALP Tier - I (21/08/2018) Morning]

Correct Answer: (b) Watt
Solution:

Power (Scalar quantity) is defined as the time rate at which work is done or energy is transferred. Formula: P = π‘Šπ‘œπ‘Ÿπ‘˜ (π‘Š) / π‘‘π‘–π‘šπ‘’ (𝑑).
1 watt = 𝐽/𝑠.

22. Which of the following has the same unit as energy? [RRB ALP Tier - I (21/08/2018) Afternoon]

Correct Answer: (d) Work
Solution:

Work is measured by the product of force and displacement of the body along the direction of the force; SI unit - Joule (J). Energy of a body is its capacity to do work; SI unit - Joule (J). Density is the mass per unit volume;
SI unit - π‘˜π‘”/π‘šΒ³.

23. The formula of Power is: [RRB ALP Tier - I (29/08/2018) Morning]

Correct Answer: (d)
Solution:

Power is the rate of doing work (SI Unit - Watt (W)). Work is the transfer of energy by a force acting on an object as it is displaced (SI Unit - Joule(J).

24. Which of the following is a unit of acceleration? [RRB NTPC CBT - II (16/06/2022) Shift 2]

Correct Answer: (a) π‘š/𝑠²
Solution:

Acceleration is the rate of change of the velocity of an object with respect to time. It is a vector quantity. Acceleration (a) =Β  𝑣 βˆ’π‘’/𝑑 , where
v - final velocity, u - initial velocity,
t - time (seconds)
β‡’ a = m/s .s β‡’ m/sΒ² . Acceleration due to gravity (g) = 9.8 m/sΒ² .

25. To change a temperature on the Kelvin scale to the Celsius scale, you have to _______ given temperature. [RRB JE 23/05/2019 (Morning)]

Correct Answer: (d) Subtract 273 from
Solution:

Temperature is the measure of the hotness or coldness of an object or material. It is measured in Celsius (Β°C), Kelvin (K) and Fahrenheit (Β°F). Kelvin is the SI unit of temperature.
Relation between celsius, Kelvin and
Fahrenheit : 𝐹 βˆ’ 32/180 = 𝐢/100 = 𝐾 βˆ’ 273/100.

26. 2500 watts = ______ kW [RRB Group D 26/09/2018 (Afternoon)]

Correct Answer: (a) 2.5
Solution:

1 kW = 1000 watts. watt (W) is the SI Unit of Power.

27. 1 kWh = ? [RRB Group D 03/10/2018 (Afternoon)]

Correct Answer: (d) 3600000 J
Solution:

1 watt-sec is a joule a watt expended for a second. Because there’s 3600 seconds in an hour, then 3600 Ws = 1 Wh = 3600 joules = 3.6 kJ
So, 1000 Wh = 1 kWh = 1000 Γ— 3.6 kJ = 3.6 Γ— 10⁢ .

28. Complete the following. 1 kWh =_______ ? [RRB Group D 29/10/2018 (Morning)]

Correct Answer: (c) 3.6 Γ— 10⁢ J
Solution:

1 kWh = (1000 W) Γ— (3600 s) = 3.6 Γ— 10⁢ J

29. 4.2 kWh = ? [RRB Group D 05/12/2018 (Morning)]

Correct Answer: (b) 15.12 Γ— 10⁢ J
Solution:

∡ 1 kWh = 1 kW Γ— 1h = 1000 W Γ— 3600 s
= 3.6 Γ— 10⁢ Ws = 3.6 Γ—10⁢J.
or, 1 kWh = 3.6 Γ—10⁢J.
Now, 4.2 kWh = 4.2 Γ— 3.6 Γ—10⁢ J
= 15.12 Γ—106 J.

30. One Watt = ? [RRB ALP Tier - I (17/08/2018) Morning]

Correct Answer: (b) 1 joule/Sec
Solution:

1 Joule is the π½π‘œπ‘’π‘™π‘’ 𝑠𝑒𝑐 amount of work done when a force of one Newton displaces a body one meter in the direction of the force applied. S.I. unit of work - Joule.
1 joule = 10⁷ erg.
1 kWh = 3. 6 Γ— 10⁢ J.