Define tension force.

Two masses connected in series with two massless strings are hanging from a support as shown in the figure. Find the tension in the upper string

Which of the following are the units of pressure?

$1$) Bar 

$2$) Torr 

$3$) mm of Hg

$4$) Pascal

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A man of mass $m$ stands on a crate of mass $M$. He pulls on a light rope passing over a smooth light pulley. The other end of the rope is attached to the crate. For the system to be is equilibrium, the force exerted by the man on the rope will be

A block of mass $m$ is suspended by a light thread from an elevator. The elevator is accelerating upward with uniform acceleration $a$. The work done by tension on the block during $t$ seconds is $(u=0):$

Which of the following statements is/are INCORRECT?

1. Pressure decreases friction.
2. The rough surface has less friction.
3. Wheels reduce friction.

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