# 7 Lecture

## PHY101

### Midterm & Final Term Short Notes

## Work and Energy

Work is defined as the product of the force and displacement of an object in the direction of the force. This means that work can only be done by a force that is applied in the same direction as the displacement of the object.

**Important Mcq's**

Midterm & Finalterm Prepration

Past papers included

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**Which of the following is a unit of work?**

A) Joule

B) Watt

C) Newton

D) Kilogram

Answer: A) Joule

**Which type of energy is possessed by an object at rest?**

A) Kinetic energy

B) Potential energy

C) Thermal energy

D) Electrical energy

Answer: B) Potential energy

**What is the work done on an object when a force is applied to it but it does not move?**

A) Positive work

B) Negative work

C) Zero work

D) Cannot be determined

Answer: C) Zero work

**A force of 10 N is applied to an object and it moves a distance of 5 m in the direction of the force. What is the work done on the object?**

A) 5 J

B) 10 J

C) 20 J

D) 50 J

Answer: C) 20 J

**Which of the following is a non-conservative force?**

A) Gravitational force

B) Spring force

C) Frictional force

D) Electrostatic force

Answer: C) Frictional force

**What is the difference between kinetic energy and potential energy?**

A) Kinetic energy depends on the position of the object, while potential energy depends on its motion.

B) Kinetic energy is the energy possessed by an object due to its motion, while potential energy is the energy possessed by an object due to its position.

C) Kinetic energy is a conservative force, while potential energy is a non-conservative force.

D) Kinetic energy and potential energy are the same thing.

Answer: B) Kinetic energy is the energy possessed by an object due to its motion, while potential energy is the energy possessed by an object due to its position.

**What is the unit of power?**

A) Joule

B) Watt

C) Newton

D) Kilogram

Answer: B) Watt

**What is the law of conservation of energy?**

A) Energy can be created but not destroyed.

B) Energy can be destroyed but not created.

C) Energy can neither be created nor destroyed, only transformed from one form to another.

D) Energy is only conserved in closed systems.

Answer: C) Energy can neither be created nor destroyed, only transformed from one form to another.

**A body of mass 2 kg is moving with a velocity of 5 m/s. What is its kinetic energy?**

A) 12.5 J

B) 25 J

C) 50 J

D) 125 J

Answer: B) 25 J

**A force of 20 N is applied to an object which moves a distance of 2 m against a frictional force of 5 N. What is the net work done on the object?**

A) 10 J

B) 30 J

C) 40 J

D) 60 J

Answer: B) 30 J

**Subjective Short Notes**

Midterm & Finalterm Prepration

Past papers included

Download PDF
Define work done by a force on an object.

Answer: Work done by a force on an object is defined as the product of the force and the displacement of the object in the direction of the force.

What is kinetic energy?

Answer: Kinetic energy is the energy possessed by an object due to its motion. It is defined as half the product of the mass of the object and the square of its velocity.

**What is potential energy?**

**Answer: **Potential energy is the energy possessed by an object due to its position or configuration. It is dependent on the height of the object above a reference point and the force acting on it.

**State the law of conservation of energy.**

**Answer: **The law of conservation of energy states that energy can neither be created nor destroyed. It can only be transformed from one form to another.

**Define power.**

**Answer:** Power is defined as the rate at which work is done or energy is transferred. It is the product of force and velocity.

**What is the work-energy theorem?**

**Answer: **The work-energy theorem states that the work done by the net force on an object is equal to the change in its kinetic energy.

**State the difference between conservative and non-conservative forces.**

**Answer: **Conservative forces are those which do not dissipate the energy of a system and are dependent only on the initial and final positions of the object. Non-conservative forces are those which dissipate the energy of a system, such as friction.

**What is the law of conservation of mechanical energy?**

**Answer: **The law of conservation of mechanical energy states that the sum of the kinetic and potential energy of a system remains constant if only conservative forces act on the system.

**How is work related to potential energy?**

**Answer: **Work done by a conservative force can change the potential energy of an object. The work done by the force is equal to the negative of the change in potential energy.

**What is the principle of work and energy?**

**Answer:** The principle of work and energy states that the work done by all forces acting on a system is equal to the change in its kinetic energy and the change in its potential energy.

### Work and Energy

Work and energy are two important concepts in physics that help us understand the behavior of objects in motion. Work is the measure of the amount of energy transferred to or from an object as a result of a force acting on it. Energy, on the other hand, is the ability to do work. Work is defined as the product of the force and displacement of an object in the direction of the force. This means that work can only be done by a force that is applied in the same direction as the displacement of the object. If the force is applied perpendicular to the displacement, no work is done. The SI unit of work is the joule (J), which is defined as the work done by a force of one newton (N) acting over a displacement of one meter (m) in the direction of the force. Energy is classified into two main types: kinetic energy and potential energy. Kinetic energy is the energy possessed by an object due to its motion. It is calculated as half of the product of the mass and the square of the velocity of the object. The SI unit of kinetic energy is also joule (J).### Potential energy,

On the other hand, is the energy possessed by an object due to its position or configuration. There are several types of potential energy, including gravitational potential energy, elastic potential energy, and electric potential energy. Gravitational potential energy is the energy possessed by an object due to its position in a gravitational field. It is calculated as the product of the mass of the object, the acceleration due to gravity, and the height above a reference level. Elastic potential energy is the energy possessed by a stretched or compressed spring, and it is calculated as half of the product of the spring constant and the square of the displacement. Electric potential energy is the energy possessed by an electrically charged object due to its position in an electric field. The principle of conservation of energy states that energy cannot be created or destroyed, but it can be transformed from one form to another. This means that the total energy of a closed system remains constant. The work-energy theorem states that the net work done on an object is equal to the change in its kinetic energy. This means that the work done on an object by a force is equal to the increase in its kinetic energy. This theorem is useful in solving problems involving the motion of objects. Another important concept related to work and energy is power. Power is the rate at which work is done or energy is transferred. The SI unit of power is the watt (W), which is defined as one joule per second (J/s).**In summary,**work and energy are important concepts in physics that help us understand the behavior of objects in motion. Work is the measure of the amount of energy transferred to or from an object as a result of a force acting on it, while energy is the ability to do work. Kinetic energy and potential energy are the two main types of energy, and the principle of conservation of energy states that energy cannot be created or destroyed, but can be transformed from one form to another. The work-energy theorem and power are also important concepts related to work and energy. Overall, understanding work and energy is essential in solving problems related to the motion of objects and systems, and it is a fundamental concept in physics.