Question

A book of mass 20g is placed on a table. Find the thrust exerted by the book on the table. (Take acceleration due to gravity as ${\text{10m}}{{\text{s}}^{{\text{ - 2}}}}$).
(A) 0.1N
(B) 0.2N
(C) 0.3N
(D) 0.4N

Answer 1

Hint: This could be simply solved by breaking the diagrams into simple free body diagrams of both the blocks. Then we need to apply Newton’s law of motion.
Formula used: Here, we will use the basic formula NLM-2:
${\text{Thrust force = F = ma}}$
Here, ${\text{F}}$ is the force exerted by the book.
${\text{m}}$ is the mass of the book
${\text{a}}$ is acceleration of the book

Complete step by step answer:
We already know that the book is on the table,
Mass of the book is $20g = 0.020kg$
It is given that the acceleration of the book to be ${\text{a = g}}$,
Thrust exerted is the force exerted,
A book exerts a force equal to its gravitational weight on the table on which it is placed through the surface of contact.
UsingNLM-2:
${\text{F = ma}}$
For the system:
${\text{Thrust = 0}}{\text{.020kg *10m}}{{\text{s}}^{{\text{ - 2}}}}{\text{ = 0}}{\text{.200N}}$
Then we need to match the correct option.

The correct option is B.

Additional Information : Thrust is a force or a push. When a system pushes or accelerates mass in one direction, there is a thrust (force) just as large in the opposite direction. In math and physics, this is described by Isaac Newton's second and third laws. Thrust is used to describe how strongly an engine pushes.

Note: It should always be kept in mind that we should always draw the FBD of body before solving any force questions. Also, we should never forget to assume tension force away from the body wherever there is rope in pulley or block questions. Similarly, spring forces also are a case of springs acting tensile (away) from the body. Also, if the bodies are connected together, they will have the same acceleration.