Answer:
20 J
Explanation:
Given:
Weight of the book is, 
Height or displacement of the book is, 
The work done on the book to raise it to a height of 2 m on a shelf is against gravity. The gravitational force acting on the book is equal to its weight. Now, in order to raise it, an equal amount of force must be applied in the opposite direction.
So, the force applied by me should be equal to weight of the body and in the upward direction. The displacement is also in the upward direction.
Now, work done by the applied force is equal to the product of force applied and displacement of book in the direction of the applied force.
Therefore, work done is given as:

Therefore, the work done to raise a book to a height 2 m from the floor is 20 J.
Answer:
The force is 
Explanation:
The moment of Inertia I is mathematically evaluated as

Substituting
for M(Mass of the wheel) and
for
(Radius of wheel)


The torque on the wheel due to net force is mathematically represented as

Substituting 135 N for
(Force acting on sprocket),
for
(radius of the chain) and F is the force acting on the sprocket due to the chain which is unknown for now

This same torque due to the net force is the also the torque that is required to rotate the wheel to have an angular acceleration of
and this torque can also be represented mathematically as

Now equating the two equation for torque
Making F the subject

Substituting values


B, this is because the particles in a solid such as the diamond can not move and even though they are locked into place they still vibrate
Answer:
The false statement is in option 'd': The center of mass of an object must lie within the object.
Explanation:
Center of mass is a theoretical point in a system of particles where the whole mass of the system is assumed to be concentrated.
Mathematically the position vector of center of mass is defined as

where,
is the position vector of the mass dm.
As we can see for homogenous symmetrical objects such as a sphere,cube,disc the center of mass is located at the centroid of the shapes itself but in many shapes it is located outside the body also.
Examples of shapes in which center of mass is located outside the body:
1) Horseshoe shaped body.
2) A thin ring.
In many cases we can make shapes of bodies whose center of mass lies outside the body.
Answer:
I think it's C I'm so sorry if I'm wrong.
Explanation: