Select the correct answer. Which statement about pneumatic systems is true?
A.
Pneumatic systems generate greater force than hydraulic systems.
B.
Pneumatic systems are safe to use at any level of pressure.
C.
Pneumatic systems are more expensive than hydraulic systems.
D.
Pneumatic systems are cleaner than hydraulic systems.

D. Pneumatic systems are cleaner than hydraulic systems.

Explanation:

pneumatics are air based systems while hydraulics are oil bases, which can get messy.

weight of the box is given as

here this is placed on the inclined of angle 42 degree

now this weight will have two components one is along the incline other is perpendicular to it

so here we need to apply a force parallel to incline opposite to its component of weight

so here the component of weight is given as

here we have

so it requires 75 n force to move it upwards

it's when something is going so fast it makes a loud noise, breaking the sound barrier, for example: a jet makes a loud noise, not only cause of the jet but because they reached a point where they went so fast that you can year the noise from various parts, kinda like a police car, lets say the car was going   so fast that you hear the siren of the cop car right next to you, but the car is probably a mile a way, it's cos the siren was next to you a few seconds if you understand me