Consider a drop of rain water having mass 1 g falling from a height of 1 km. It hits the ground with a speed of 50 m/s. Take g constant with a value 10 m/s2. The work done by the (i) gravitational force and the (ii) resistive force of air is

• (i) – 10 J (ii) –8.25 J

• (i) 1.25 J (ii) –8.25 J

• (i) 100 J (ii) 8.75 J

• (i) 100 J (ii) 8.75 J

The diagrams below show regions of equipotentials

A positive charge is moved from A to B in each diagram.

• Maximum work is required to move q in figure (c).

• In all the four cases the work done is the same.

• Minimum work is required to move q in figure (a).

• Minimum work is required to move q in figure (a).

If force $\overrightarrow{\mathrm{F}}=5\hat{\mathrm{i}}+3\hat{\mathrm{j}}+4\hat{\mathrm{k}}$ makes a displacement of $\overrightarrow{\mathrm{s}}=6\hat{\mathrm{i}}-5\hat{\mathrm{k}}$work done by the force is

• 10units

• $122\sqrt{5}$units

• $5\sqrt{122}\mathrm{units}$

• 20units

The work done in pulling up a block of wood weighing 2 kN for a length of 10 m on a smooth plane inclined at an angle of 15° with the horizontal is

• 9.82 kJ

• 89 kJ

• 4.35 kJ

• 5.17 kJ

$$\begin{gathered} \mathrm{A} \mathrm{particle} \mathrm{moves} \mathrm{from} \mathrm{postion} \\ \overrightarrow{{\mathrm{r}}_1}=3\hat{\mathrm{i}}+2\hat{\mathrm{j}}-6\hat{\mathrm{k}} \mathrm{to} \mathrm{position} \overrightarrow{ {\mathrm{r}}_2}=14\hat{\mathrm{i}}+13\hat{\mathrm{j}}+9\hat{\mathrm{k}} \mathrm{under} \mathrm{action} \mathrm{of} \mathrm{force} \\ \overrightarrow{\mathrm{F}}=4\hat{\mathrm{i}}+\hat{\mathrm{j}}+3\hat{\mathrm{k}} \mathrm{N}. \mathrm{The} \mathrm{work} \mathrm{done} \mathrm{will} \mathrm{be} \end{gathered}$$

• 100J

• 50J

• 200J

• 75J