Final answer:
The work done on a barrel against gravity is calculated by multiplying the weight of the barrel by the vertical distance it is raised. For a barrel weighing 2000 N and raised 0.80 m in height, the work done is 1600 Joules. So, the correct option is b.
Step-by-step explanation:
The work done on the barrel against gravity can be calculated using the formula for work done (W), which is the product of the force (F) acting on an object and the distance (d) moved by the force in the direction of the force. Mathematically, it is represented as W = F × d × cos(θ), where θ (theta) is the angle between the direction of the force and the direction of motion. When a force is applied vertically to lift something horizontally, θ becomes 0° and the cosine of 0° is 1. Therefore, the work done is simply the product of the force and the vertical distance.
For the barrel, the force due to gravity is the weight of the barrel, which is 2000 N, and the vertical distance is the height of the lorry’s back from the road, which is 0.80 m. The calculation thus becomes W = 2000 N × 0.80 m, which equals to 1600 Joules. So, the correct option is (b) 1600 J.