NCERT Class 11 Physics Solutions: Chapter 5 – Laws of Motion Part 11

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Question 5.30:

An aircraft executes a horizontal loop at a speed of with its wings banked at What is the radius of the loop?

Answer:

Speed of the aircraft,

Acceleration due to gravity,

Angle of banking,

For radius , of the loop, we have the relation:

Question 5.31:

A train runs along an unbanked circular track of radius at a speed of . The mass of the train is . What provides the centripetal force required for this purpose of the engine or the rails? What is the angle of banking required to prevent wearing out of the rail?

Answer:

Radius of the circular track,

Speed of the train,

Mass of the train,

The centripetal force is provided by the lateral thrust of the rail on the wheel. As per Newton’s third law of motion, the wheel exerts an equal and opposite force on the rail. This reaction force is responsible for the wear and rear of the rail

The angle of banking , is related to the radius and speed by the relation:

Therefore, the angle of banking is about

Question 5.32:

A block of mass is raised by a man in two different ways as shown in Figure. What is the action on the floor by the man in the two cases? If the floor yields to a normal force of which mode, should the man adopt to lift the block without the floor yielding?

A block of mass is raised by a man in two different ways

A Block of Mass is Raised by a Man in Two Different Ways

Answer:

and in the respective cases; Method

Mass of the block,

Mass of the man,

Acceleration due to gravity,

Force applied on the block,

Weight of the man,

Case (a): When the man lifts the block directly:

In this case, the man applies a force in the upward direction. This increases his apparent weight.

Action on the floor by the man

Case (b): When the man lifts the block using a pulley:

In this case, the man applies a force in the downward direction. This decreases his apparent weight.

Action on the floor by the man

If the floor can yield to a normal force of then the man should adopt the second method to easily lift the block by applying lesser force.