laws of motion Questions

A truck is stationary and has a bob suspended by a light string in a frame attached to the truck. The truck suddenly moves to the right with an acceleration of $a$. In the frame of the truck, the pendulum will tilt:

A body of mass $m$ is kept on a rough horizontal surface (coefficient of friction = $\mu$). A horizontal force is applied to the body, but it does not move. The resultant of normal reaction and the frictional force acting on the object is given by $\vec{F}$ where:

An object flying in the air with velocity $(20\hat{i}+25\hat{j}-12\hat{k})$ suddenly breaks into two pieces whose masses are in the ratio of $1:5$. The smaller mass flies off with a velocity $(100\hat{i}+35\hat{j}+8\hat{k})$. The velocity of the larger piece will be: