Q1: Define Work. State its unit.
Ans: Work is said to be done when a force acts on a body and the body moves in the direction of force.
Unit of work is Joule (J).
Q2: Define Joule.
Ans: One joule is the amount of work done when a force of 1 newton moves a body through a distance of 1 meter in the direction of force.
Q3: Write the formula to calculate Work done.
Ans: Work done formula:
W = F × d × cosθ
Q4: Define Energy. State its unit.
Ans: Energy is the capacity to do work.
Unit of energy is Joule (J).
Q5: State the types of Energy.
Ans: The types of energy are:
- ➔ Kinetic energy
- ➔ Potential energy
Q6: Define Kinetic Energy.
Ans: Kinetic energy is the energy possessed by a body due to its motion.
Q7: Define Potential Energy.
Ans: Potential energy is the energy possessed by a body due to its position or state.
Q8: A car of mass 1200kg is moving with a velocity of 80 km/h. Find its kinetic energy.
Ans: Given:
Mass, m = 1200 kg
Velocity, v = 80 km/h = (80 × 1000) / 3600 = 22.22 m/s
Formula:
KE = (1/2) m v2
Step 1: Substitute values
KE = (1/2) × 1200 × (22.22)2
Step 2: Calculation
KE = 600 × 493.7
KE = 296220 J
Final Answer:
Kinetic Energy ≈ 2.96 × 105 J
Q9: State the Work Energy Relation.
Ans: The work energy relation states that work done on a body is equal to the change in its kinetic energy.
Q10: Define Power. State its Unit.
Ans: Power is the rate of doing work or rate of transfer of energy.
Unit of power is Watt (W).
Q11: State the formula to calculate Power.
Ans: Formula:
P = W / t
Q12: Define Watt.
Ans: One watt is the power when 1 joule of work is done in 1 second.
Q13: Define Horse Power.
Ans: Horse power is a unit of power used in engineering.
1 HP = 746 watts.
Q14: State the Relation between Watt and Horse Power.
Ans: 1 Horse Power = 746 Watts
Q15: Define Indicated Horse Power (I.H.P).
Ans: Indicated Horse Power is the power developed inside the cylinder of an engine.
Q16: Define Brake Horse Power (B.H.P).
Ans: Brake Horse Power is the actual power available at the output shaft of an engine.
Q17: Define Dynamometer. Write its types.
Ans: A dynamometer is a device used to measure power of an engine.
Types:
- ➔ Absorption dynamometer
- ➔ Transmission dynamometer
Q18: What is an Absorption Dynamometer?
Ans: An absorption dynamometer absorbs the power produced by the engine and converts it into heat.
Q19: What is a Transmission Dynamometer?
Ans: A transmission dynamometer measures power while it is being transmitted from the engine to the load.
Q20: What is a Prony Brake Dynamometer?
Ans: A Prony brake dynamometer is an absorption type dynamometer used to measure engine power by friction braking.
Q21: What is a Rope Brake Dynamometer?
Ans: A rope brake dynamometer is a device in which power is absorbed by a rope wrapped around a pulley.
Q22: State the uses of a Dynamometer.
Ans: The uses of a dynamometer are:
- ➔ Measuring engine power
- ➔ Testing machine performance
- ➔ Laboratory experiments
Q23: Define Power Loss.
Ans: Power loss is the difference between input power and output power of a machine.
Q24: Write the formula to find I.H.P of an engine.
Ans: Formula:
I.H.P = (P × L × A × N) / 4500
where:
P = pressure
L = stroke length
A = area
N = number of strokes
Q25: Find work in Joules done by a motor of 5 hp in 2 hours.
Ans: Given:
Power = 5 HP
Time = 2 hours
Step 1: Convert HP to Watt
1 HP = 746 W
P = 5 × 746 = 3730 W
Step 2: Convert time to seconds
t = 2 × 3600 = 7200 s
Step 3: Work formula
W = P × t
Step 4: Calculation
W = 3730 × 7200
W = 26856000 J
Final Answer:
Work done = 2.6856 × 107 J
Q26: Define Efficiency.
Ans: Efficiency is the ratio of useful output power to input power expressed in percentage.
Formula:
η = (Output / Input) × 100%
Q27: Describe the relationship between I.H.P, B.H.P and Efficiency.
Ans: Efficiency is given by:
η = (B.H.P / I.H.P) × 100%
It shows how much input power is converted into useful output power.
