Answer: 1500 Joules
Explanation: To calculate the work done by the weight lifter, we can use the formula:
Work = Force x Distance x cos(theta)
where "Force" is the force applied by the weight lifter, "Distance" is the vertical distance that the weight is lifted, and "theta" is the angle between the direction of the force and the direction of the displacement.
In this case, the force applied by the weight lifter is 1000N and the vertical distance lifted is 1.5m. Since the force is applied vertically upwards and the displacement is also vertical, the angle between the direction of the force and the direction of the displacement is 0 degrees (cos(0) = 1).
Therefore, the work done by the weight lifter is:
Work = 1000N x 1.5m x cos(0) = 1500 Joules
So the work done by the weight lifter on the weights is 1500 Joules.