Class 10                                                                     Marks: 20

Physics Revision

ATTEMPT ALL QUESTIONS.

Define moment of force. Write relationship between the SI and CGS unit of moment of couple. 2

Find the mass of the scale in equilibrium .  

                                      

Draw diagrams and locate the centre of gravity  of hollow cone and triangular sheet. 2

 State the  type of work done by a coolie  when i)  he lifts a load up ii) when he moves on a horizontal platform carrying load on his head.     2

A force is applied on a body of mass 20kg movong with a velocity of 40 m/s. The body attains a velocity of 50 m/s in 2  s. Calculate the work done by the force. 2

Give one example of  each  i) when chemical energy is converted into electrical energy .

                                                  Ii when electrical energy changes into sound  energy.   2

A ball of mass  200g is thrown vertically upwards with initial velocity of 20 m/s. Calculate its maximum potential energy.       2

State law of conservation of energy and prove it for a feely falling body taking any two points in the fall. 3

Give two conditions for which a force does no work. 2

Refractive index and colour of a light

 Red colour has longest wavelength so it has maximum speed in a medium compared to other colours.  As it travels with maximum speed in a medium,  the refractive index of the medium for Red colour is minimum.

MECHANICAL ADVANTAGE , VELOCITY RATIO

Which is always constant for a machine of given design: MA or VR ?

Ans: VR remains constant for a machine of given design as it depends on the distances moved by the load and effort but MA can vary due to the friction developed between the moving parts of the machine.

LENZ'S LAW

LENZ'S LAW is based on law of conservation of

a) mass

b) charge

c) momentum 

d) energy.

Ans: d)   energy 

Why is uniform circular motion an accelerated motion?

 Q: Why is uniform circular motion an accelerated motion?

A: The velocity of  Uniform Circular motion changes continuously due to its changing direction. As there is change in velocity, the motion is accelerated motion.

DOOR HANDLES

 Question: Why are door handles fitted at the edge of the door ?

Answer: Door handles are fitted at the edge to increase  the perpendicular distance of the force from the axis of rotation so that the minimum force can be applied to achieve the given torque.