Net Force

Q.

A charge $q$ is placed at the centre of the line joining two equal charges $Q$. The system of the three charges will be in equilibrium, if $q$ is equal to

1. $-\frac{Q}{2}$

2. $-\frac{Q}{4}$

3. $+\frac{Q}{4}$

4. $+\frac{Q}{2}$

Q.

The resultant of two forces acting on a body is zero if the forces are:

1. Equal in magnitude and opposite in direction.

2. Equal in magnitude.

3. Opposite in direction.

4. Unequal in magnitude and opposite in direction.

Q. A block is kept at rest on a horizontal surface. We can say that:

1. no force is acting on the block
2. speed of the block is increasing
3. no net force is acting on the block
4. speed of the block is decreasing

Q. write the CGS unit of force.

Q. <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--> Define moment of a force and state its SI unit.

Q. Define moment of couple. Write its S.I unit.

Q. 1) A walnut can be broken by applying a direct force of 50 kgf. If the walnut is placed in a nut cracker , the length of whose handle is 18 cm and nut is placed 2 cm from the pivot , calculate the minimum force required to crack the nut.