Railway Science (Physics-Work, Energy and Power) (Part-III)

Total Questions: 50

1. Match the following with the correct answer: [RRB ALP Tier - I (30/08/2018) Evening]

Codes:

1234
(a)DACB
(b)BACD
(c)DCBA
(d)DCAB
Correct Answer: (a)
Solution:

Work - It is the product of the component of the force in the direction of the displacement and the magnitude of this displacement. Battery is the collection of one or more cells whose chemical reactions create a flow of electrons in a circuit.

2. Match the following with the correct response: [RRB ALP Tier - I (31/08/2018) Morning]

Codes:

1234
(a)ACBD
(b)DBCA
(c)ACDB
(d)ABCD
Correct Answer: (a)
Solution:

Work : Product of the component of the force in the direction of the displacement and the magnitude of this displacement (Work = Force × displacement × cosθ). Units of work : Joule, Newton meter

3. Which of the following is NOT an example of potential energy? [RRB ALP Tier - I (31/08/2018) Afternoon]

Correct Answer: (a) Running water
Solution:

Potential energy - Energy possessed by a body by virtue of any object’s position relative to others. Example - Pendulum (If a pendulum is held at one end, it has the maximum potential energy at that time due to its position), Bow & Arrow, Rock At Cliff’s Edge, Rollercoaster.

4. Which of the following can do more work? [RRB ALP Tier - I (31/08/2018) Evening]

Correct Answer: (b) A moving bullet
Solution:

The work done by the bullet will be more as compared to a rotating wheel, a speeding stone, and a raised hammer because an object that moves faster can do more work than an identical object moving relatively slowly. The amount of work depends on factors like mass, velocity, and the nature of the work being performed.

5. In which of the following mentioned activities is the potential energy (P.E.) converted into kinetic energy (K.E.)? [RRB ALP Tier - I (31/08/2018) Evening]

Correct Answer: (d) The swinging of a pendulum
Solution:

In the case of a swinging pendulum, as the pendulum reaches its highest point in the swing (maximum potential energy), it possesses the potential to do work. As it descends from that point, the potential energy is converted into kinetic energy as the pendulum gains speed and velocity. At the lowest point of the swing, the pendulum has the maximum kinetic energy and minimum potential energy. The continuous swinging of the pendulum involves the back-and-forth conversion of potential energy to kinetic energy and vice versa.

6. A force increases the speed of a 1.0 kg object from 4 m/s to 8 m/s. The work done by the force will be ___________ . [RRB Group D 17/09/2018 (Morning)]

Correct Answer: (c) 24 J
Solution:

7. A person lifts luggage of 20 kg from the ground and puts it on his head 2 m above the ground. Calculate the work done by him. (g = 10 ms⁻²) [RRB Group D 17/09/2018 (Afternoon)]

Correct Answer: (b) 400 J
Solution:

Work (W) = Force (F) × Displacement (d) Since, Force = Mass × Acceleration Therefore, W = Mass × Acceleration × Displacement = 20 kg × 10 ms⁻² × 2 m = 400 kg m⁻² s⁻² = 400 J.

8. A person does some work of 1,000 J in 2 s. His power will be ___________. [RRB Group D 17/09/2018 (Afternoon)]

Correct Answer: (c) 500W
Solution:

Power = 𝑊𝑜𝑟𝑘 𝑑𝑜𝑛𝑒 /  𝑇𝑖𝑚𝑒 𝑡𝑎𝑘𝑒n = 1000/2 =  500 J/s = 500 W.

9. 9800 joules of energy was spent to raise a mass of 70 kg. The mass was raised to a height of : [RRB Group D 17/09/2018 (Evening)]

Correct Answer: (c) 14 m
Solution:

Gravitational potential energy (E) = mgh
Given m = 70 kg, g = 10 m/s² ,  , E = 9800 J
Height (h) =  𝐸/𝑚𝑔 ⇒ 9800/70×10 ⇒ 14 m.

10. A 40 kg girl runs up a flight of stairs having a rise of 5 m in 4 s. The power developed by her will be____.(take g= 10 m/s²) [RRB Group D 18/09/2018 (Morning)]

Correct Answer: (c) 500W
Solution:

Given : Mass (m) = 40 kg, g = 10 m/s² ,
Time (t) = 4s, Height (h) = 5 meter,
∵ Potential energy (U) = mgh
So, U = 40 × 10 × 5 = 2000 J
Power = 𝑊𝑜𝑟𝑘 𝑑𝑜𝑛𝑒/𝑡𝑖𝑚𝑒
P = 2000/4 =  500 W.