Hello candidate,

1. The handle open the door is always provided at the age of a dog because if it is provided at the lock them then it would not be able to generate enough call in order to provide a rotational motion to the door in order to open it.

2. If two masses on moving with velocities V1 and V2, then the velocity of centre of mass is equal to m1V1 + m2V2/ (m2+M1).

3. Normal reaction refers to a equal and opposite for switch the body produces upon which the forces acting upon.

Hope this information helps you!!