# (Important Questions) CBSE Important Questions For Physics Class IX

**CBSE Important Questions For Science Class IX**

**Q.1.** what is persistence of hearing? (1)

**Q.2.** what does the slope of speed-time
graph indicate? (2)

**Q.3.** what is one Newton? (1)

**Q.4.** why will a sheet of paper fall lower
than one that is crumpled into a ball? (2)

**Q.5**. A stone is dropped from the edge of a
roof.

- How long does it take to fall 4.9m?

- How fast does it move at the end of that fall?

- How does it move at the end of 7.9m?

- What is its acceleration after 1 second and after 2 second? (4)

**Q.6.** A boy and a girl do the same work in 5
min and 10 min respectively. Which of these has more power and why? (1)

**Q.7. (a)** What name has been given to the
force with which two objects lying a part attract each other?

**(b)** What happens to the gravitational force
between two objects when the distance between them is:

**(i) **doubled

**(ii)** half (2)

**Q.8.** **(a)** what is the
condition for a force to do work on a body?

**(b)** A boy throws a rubber ball vertically upwards. What type of
work, positive or negative is done.

**(i)** By force applied by boy?

**(ii)** By the gravitational force of earth? (3)

**Q.9.** name the characteristics of sound
which depends on:

**(i)** Amplitude

**(ii)** waveform

**Q.10.** give one use of ultrasound in
industry and one in hospitals? (1)

**Q.11.** A sonar station picks up a return
signal after 3seconds. How far away is object? (speed of sound in water=1440m/s)
(1)

**Q.12**. Name that part of ear which vibrates
when outside sound fall on it? (1)

**Q. 13. **When the passenger m oving in a bus
, the road side trees appear to b e moving ----------------------------------
(a) Back ward (b)For ward

**Q. 14. **In uniform motion the object covers
------------ (a) equel distance (b) un equal distance

**Q. 15. **Where objects cover un equal
distances in equal interval of time then the motion is called ----------------
(a) uniform motion (b) non uniform motion

**Q. 16. **The average speed = =A car
accelerate = (a) Total time taken /total distance traveled (b) Total distance
traveled/total time taken

**Q. 17. **v = (a) t/s (b) s/t

**Q. 18. **An object travels 16m in 4sec and
another 16 m in 2 sec. what is the average speed of the object----------- (a)
5.33 ms-1 (b) 5. 34 ms-1

**Q. 19. **If we specify , its direction of
motion along with its speed , the quantity that specifies with the aspects is
called------------- (a) velocity (b) motion

**Q. 20. **Automobiles are fitted with a device
that show the distance traveled . such a device is known ---------- (a) odometer
(b) Speedo meter

**Q. 21. **The velocity of an object can be
-------------- (a) non uniform or variable (b) uniform or variable

**Q. 22. **Average velocity = (a) initial
velocity + final velocity/ 2 (b) initial velocity + final velocity/1

**Q. 23. **Average velocity = (a) placement/
total time taken (b) Displacement/ total time taken

**Q. 24. **Acceleration = (a) change in
velocity/ time taken (b) change in motion / time

**Q. 25. **S = (a) ut + 1/2at^{2} (b)
ut + 1 at^{2}

**Q. 26. **A car accelerate uniformly from 18
km h^{-1} to 36 km h^{-1} in 5 sec . calculate the
acceleration------------- (a) 1ms^{-2}(b) 1 ms^{-3}

**Q. 27. **A train starting from rest attaind a
velocity of 72 km h^{-1} in 5 minutes . Assuming that the acceleration
is uniform. Find the distance traveled by the train for attaing this velocity
--------------------------------- (a) 2km (b) 5 km

**Q . 28. **Define SI unit of force.(1)

**Q . 29. **A body is moving with a uniform
speed of 15 m/s on a circular track. Why is its motion called acceleration
motion.(1)

**Q . 30. **What is the distance travelled and
displacement of a body as its moves from A to B via C.(2)

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**Q . 31. **A motor boat starting from rest on
a lake accelerates in a straight line at a constant rate of 2m/s2 for 4 seconds.
How far does the boat travels during this time.(2)

**Q . 32. **Name the force which keeps various
planets in their orbits. Write down the formula for the force which exists
between two bodies of mass m1 and m2 separated by a distance R from each
other.(2)

**Q . 33. **State Newton’s second law of
motion. A ball is thrown on a smooth surface with a force and it stops after
some time. Is it supporting First law of motion. Give reasons for your
answers.(2)

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**Q . 34. **Velocity-time graph of a body is
given above. Answer the following questions (3)

- Which part of the graph shows uniform acceleration.
- Which part of the graph shows uniform retardation.
- Calculate the total distance travelled by the body.
- Which part of the graph shows zero acceleration.(3)

**Q . 35.**

- Derive the first equation of motion v=u + at graphically.
- Write the equation describing the principle of conservation of momentum.
- Why does the Gun recoil when a bullet is fired from it. (5)