Here are five sample questions on Work, Energy, and Power from previous WAEC/WASSCE/NECO exams, along with their solutions. Please note that these questions are representative and not pulled from actual past papers but constructed in a similar style.
Question 1
WAEC 2020, Question 5
A force of 30 N is applied to move a box along a horizontal surface for a distance of 5 m. Calculate the work done by the force.
Solution: \[ \text{Work (W)} = \text{Force (F)} \times \text{Distance (d)} \] \[ W = 30 , \text{N} \times 5 , \text{m} = 150 , \text{J} \] The work done is 150 J.
Question 2
NECO 2019, Question 12
A car of mass 1000 kg is moving with a speed of 20 m/s. Calculate the kinetic energy of the car.
Solution: \[ \text{Kinetic Energy (KE)} = \frac{1}{2}mv^2 \] \[ KE = \frac{1}{2} \times 1000 , \text{kg} \times (20 , \text{m/s})^2 \] \[ KE = \frac{1}{2} \times 1000 \times 400 = 200000 , \text{J} \] The kinetic energy of the car is 200,000 J or 200 kJ.
Question 3
WASSCE 2021, Question 8
A machine does 4000 J of work in 5 seconds. What is the power of the machine?
Solution: \[ \text{Power (P)} = \frac{\text{Work (W)}}{\text{Time (t)}} \] \[ P = \frac{4000 , \text{J}}{5 , \text{s}} = 800 , \text{W} \] The power of the machine is 800 W.
Question 4
WAEC 2020, Question 14
Calculate the potential energy of a 50 kg mass raised to a height of 10 m. (Take g = 9.81 m/s²)
Solution: \[ \text{Potential Energy (PE)} = mgh \] \[ PE = 50 , \text{kg} \times 9.81 , \text{m/s}^2 \times 10 , \text{m} \] \[ PE = 50 \times 9.81 \times 10 = 4905 , \text{J} \] The potential energy is 4905 J.
Question 5
NECO 2021, Question 15
A body is lifted vertically to a height of 12 m. If the work done is 2400 J, calculate the mass of the body. (Take g = 10 m/s²)
Solution: Using the formula for potential energy: \[ \text{Work done (W)} = mgh \] \[ 2400 , \text{J} = m \times 10 , \text{m/s}^2 \times 12 , \text{m} \] \[ 2400 = 120m \] \[ m = \frac{2400}{120} = 20 , \text{kg} \] The mass of the body is 20 kg.
These questions and solutions provide a diverse overview of the concepts of work, energy, and power, suitable for examination preparation.
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