Get the CBSE Class 9th Science chapter, Work and Energy: Important topics and questions to prepare for Class 9 Science Examination, 2017-2018. This will provide you with a very clear idea about what type of questions are being framed for the exam and from which topics. The pattern in which the question paper is set is quite different from the style in which the course structure is actually defined. Consider the below mentioned terms/questions at the time of preparation.
Find below the important terms/topics to revise from chapter-Work and Energy:
- Why do living beings and machines need energy?
- Definition of work in reference of science (physics)
- Commercial unit of energy
- Scientific concept of work
- Work done= F x S; here it is very important to know that “S” is not distance but displacement
- A force of 5 N is acting on an object. The object is displaced through 2 m in the direction of the force. If the force acts on the object all through the displacement, then what is the work done in this case?
- Conditions to ensure either work are positive negative or zero.
- Units of work
- Define energy and also mention the different forms of energy
- Derivation and expression of potential energy and kinetic energy
- Law of conservation of energy
- A body is falling freely from a height “H”. Prove the law of conservation of energy at different places (Very Important)
- Formula and units of power
- How much energy will be used when a 100 watt bulb is used for 10 hours?
- An electric bulb of 60 W is used for 6 hrs. daily. Calculate the ‘units’ of energy consumed in one day by the bulb.
- Define 1 J of work
- Derivation of formula of kinetic energy by using the formula V2 – U2 = 2aS
- An object of mass 15 kg is moving with a uniform velocity of 4 ms-1. What is the kinetic energy possessed by the object?
- Potential energy is path dependent or not
- Find the energy possessed by an object of mass 10 kg when it is at a height of 6 m above the ground. Given, g = 9.8 m S-2.
- All the activities given in NCERT books are very useful to understand the concepts
- Practice of all the examples from NCERT books is must
Important Questions are as below:
Q. A body of mass 2 kg is dropped from a height of 1m. Its kinetic energy as it touches the ground is _______.
- 19.6 m
- 19.6 kg
- 19.6 N
- 19.6 J
Q. A coolie carries a load of 400 N to a distance of 10 m. The work done by him is?
- 5 N
- 50.000 N
- 19.6 N
Q. Two objects of masses 1 x 10-3 kg and 4 x 10-3 kg have equal momentum. Calculate the ratio of their kinetic energies?
Q. What happens with the total energy of a freely falling body?
- Remains constant
- First increases and then decreases
Q. An object of mass m is moving with a constant velocity v. How much work should be done on the object in order to bring the object to rest?
Q. What is the relation between joule (J) and ergs (erg)?