Study Notes STD IX Physics

1. Give an example of inertia of motion.

2. 1 kgwt =………. N

3. Describe a scenario where displacement is zero, but distance is not.

4. Write any two examples of circular motion.

5. Describe the benefits of using small prisms in reflectors of motorcycles.

Answer

1.When a bus stops suddenly, the passengers tend to fall forward.

.A participant in long jump competition, runs some distance and then jumps.

.A ball set rolling on a horizontal floor keeps moving forward.

2. 1kgwt= 9.8 N

3. If a person walks 5 m north and then  m south through the same path, their displacement is zero because they end up at their starting point. However, the distance travelled is 10 m, as it is the total path length covered. This illustrates how displacement considers direction, while distance does not.

4.Motion of Artificial satellites

.Whirling a stone tied to a string

.Rotation of fan blades

5. Many small prisms are used in reflectors used in motor cycles. Light falling on the prisms undergoes total internal reflection and reflects back without loosing the intensity of light. The image can be seen with greater visual clarity.

Classify the following instances into inertia of motion and inertia of rest

a) A fan continue to rotate for a while even after it is switched off.

b) It is possible to strike out a single carrom coin without disturbing others, from a set of coins stacked one over the other.

1.Write some traffic rules for pedestrians to follow.

2. A car starting from rest travels 100 m in 5 s with uniform acceleration. Find the acceleration of the car?

3. State true or false.

a) The value of g will be the same everywhere on the earth.

b) The factors that influence the value of g are mass of the earth and radius of the earth.

4. a-Inertia of motion

b-Inertia of rest

5.Pedestrians should walk along the right side of the road.

Cross the road only at the zebra crossing, obeying the traffic signal.

Use sidewalks.

Avoid crossing between parked cars.

12. u = 0m/s

t = 5s

S =100 m

a = ?

1 s = ut + 1/2 at²

100= 0x5+1/2×a×52

a=100×2 /25 = 8 m/s²

13. a) False

b) True

16. A car then moving with uniform acceleration and changes its velocity from 10 m/s to 50 m/s in 4 second,then

a) Find out the acceleration of car?

b) Find out the displacement in this time?

16. a) a = V-u/

t = 4s

a = 50-10 /4

a = 10 m/s²

b) s = ut+1/2 at²

=10×4+ 1/2(10×4²)

= 40 + 80 = 120 m

18. State true or false.

a) All internal forces are unbalanced forces.

 

b) All internal forces are balanced forces.

 

c) All balanced forces are internal forces.

 

19. Differentiate between mass and weight.

20. 18. a) False

 

b) True

 

c) False

 

19.Mass

 

*Measured using common balance

 

*Unit kg

 

*Mass of an object is the quantity of matter contained in it.

 

*Scalar quantity

 

*Mass of an object is same everywhere

 

Weight

 

• Measured using spring balance

 

*Unit newton (N) or kgwt

 

• The weight of the object on the Earth is the gravitational force exerted by the Earth on that object.

 

• Vector quantity

 

• Weight of an object will vary from place to place

22. “A man jumps from a boat to the shore”

 

a) Identify the action and reaction in the above situation.

 

b) State the law related to the given situation.

 

c) Write another example related to this law.

22. a) Action – The boat moves backward. Reaction – The man lands on the shore.

 

b) Newton’s third law of motion.

The law states that for every action there is an equal and opposite reaction.

 

c) Recoil of a gun

 

Rowing a boat