Calculate the work done when lifting objects of different masses and heights.

$$m = 500 \text{ g} = 0.5 \text{ kg}$$ $$d = 210 \text{ cm} = 2.1 \text{ m}$$

$$W = F \times d = 4.9 \text{ N} \times 2.1 \text{ m} = 10.29 \text{ J}$$

The work done is $\boxed{\textbf{10.29 J}}$.

2. A 2kg ball is lifted 50cm from the floor. Calculate the work done.

$$W = F \times d = 19.6 \text{ N} \times 0.5 \text{ m} = 9.8 \text{ J}$$

The work done is $\boxed{\textbf{9.8 J}}$.

3. A 1500g load is lifted 2m high. Calculate the work done.

$$W = F \times d = 14.7 \text{ N} \times 2 \text{ m} = 29.4 \text{ J}$$

The work done is $\boxed{\textbf{29.4 J}}$.

4. A 3kg box is pushed 250cm across the floor. Calculate the work done.
Note: For horizontal motion, work done depends on the applied force and friction. Since no friction or applied force is given, and given the context of other problems involving lifting, we will assume the question implies the work done if the force applied is equal to the object's weight, or if it were lifted by that distance for simplification.

$$W = F \times d = 29.4 \text{ N} \times 2.5 \text{ m} = 73.5 \text{ J}$$

The work done is $\boxed{\textbf{73.5 J}}$.

5. A 750g object is lifted 1.5m high. Calculate the work done.