Questions

Here Joystick, Mouse and Scanner are Input devices through which data is given to the computers. But Headphones are output devices through which sound comes as an output from the computer or any devices.

Compressions and Rarefactions are characteristic of Longitudinal waves.

The direction of vibration of the particles is in the same plane as in which the wave is propagating. The particles vibrate back and forth, about their mean positions.

Squirrels typically build leaf nests in the summer by weaving together small branches they've gnawed off of trees. These nests are lined with grass, moss, leaves and pine needles. Both male and female gray squirrels of all ages participate in building dens.
 

Let speed of train B be x m/s And length of train B be y m
Then length of train A is 2y m
Speed of train A = 84 × 5/18 = 210/9 m/s = 70/3 m/s
A.T.Q, (2y+y)/10 = 70/3 − x .............(i)
and (2y+y)/ 22.5 = 70/3 − 2x ................(ii)
solving (i) and (ii), y = 50 m

A method for providing fault tolerance by using multiple hard disk drives

The weight of the man mg is acting on the floor. As the lift is moving up with an acceleration, say a, the man too in it is having this acceleration. The force producing this acceleration is ma. By Newton's third law, this force will have an equal reaction pressing the floor equal to ma. Therefore the total resultant reaction on the floor is mg+ma = m(g+a) which is mg, the weight of the man. So (a) is correct.