**IX CLASS PHYSICS SS2 **

1) **.**Why does a buffalo float on
the river but not the man?

2) Why does ice float on the water?

3) Why does a ship made up of iron floats but the iron sinks?

4) How do submarines float or sink as desired?

5) Why does a mug full of water appear lighter inside the water?

6) A dead body floats in water with its head immersed in water. Explain.

7) In what direction does the buoyant force on an object, due to liquid act?

8) Why does a block of plastic piece left under water cone to the surface of water?

9) Write the condition under which the body would float on a liquid?

10) The volume of a 500 g sealed packet is 350 cm3. Will the packet float or sink in water if the density of water is 1cm−3? What will be the mass of the water displaced by this packet

11) The volume of 50 g of a substance is 20 cm3. If the density of water is 1 g cm−3, will the substance float or sink?

12) Why does a block of plastic released under water come up to the surface of water?

13) what direction does the buoyant force on an object immersed in a liquid act?

14) Name the factors the buoyant force does not depend on?

15) What are the factors the buoyant force depends on?

16) A 2000 kg car traveling at 72 kmph ran into a concrete wall and stopped in 0.05 sec. What impulse did the wall exert on the car? Find Kinetic enegry of both ? Find the work done n this time ?

17) An unloaded truck weighing 2000 kg has a
maximum acceleration of 0.5 m/s^{2}. What is the maximum acceleration
when it is carrying a load of 2000 kg its starts from rest & run for 20 sec
? Find Kinetic enegry of both ? Find the
work done n this time ?

18) ** **A
bullet of mass 15g leaves the barrel of a gun with a velocity of 120m/s.The gun
recoils with a velocity of 1m/s. Find the mass of the gun. Find Kinetic enegry
of both ? Find the work done n this time ?

19) ** **A
force of 3N acts on a mass of 0.5kg at rest for 10s. Find the final velocity
and the momentum of the body after 10s. Find Kinetic enegry of both ? Find the
work done n this time ?

20) ** **A
force of 80N acting on a certain mass for 3s gives it a velocity of 6m/s. find
the mass of the body if the body was initially at rest. Find Kinetic enegry of
both ? Find the work done n this time ?

21) A toy of mass 0.1kg acquires a speed of 5 m/s when pushed forward. Ahat is the impulse given to the toy? Find Kinetic energy of both ? Find the work done n this time ?

22) ** **A
projectile weighing 200kg is fired from a gun with a velocity of 500m/s. If the
velocity of recoil of the gun is 12.5m/s calculate the mass of the gun. Find Kinetic
enegry of both ? Find the work done n
this time ?

23) ** **A
car of mass 2500kg accelerates at the rate of 4m/s2 and then at the rate of 16
m/s2. Calculate t6he ratio of the forces exerted by the engine in the two
cases. Find Kinetic enegry of both ?
Find the work done n this time ?

24) ** **A
driver accelerates his car first at the rate of 1.8m/s2 and then at the rate of
1.2m/s2 calculate the ration of the forces exerted by the engines. Find Kinetic
enegry of both ? Find the work done n
this time ?

25) ** **A
body of mass 5 kg undergoes a change in speed from 30 to 40m/s . calculate its
increase in momentum. Find Kinetic enegry of both ? Find the work done n this
time ?

26) ** **A
body of mass 100g is moving with a velocity of 15m/s Find the momentum
associated with the ball. Find Kinetic enegry of both ? Find the work done n this
time ?

27) ** A **body of mass 5 kg is moving
with a uniform velocity of 10m/s It is acted upon by a force of 20N What will
be its velocity after 1s. Find Kinetic enegry of both ? Find the work done n this
time ?

28) ** **In
order to gain a velocity of 12m/s how long should a force of 30N be exerted on
a body of mass 5kg? Find Kinetic enegry
of both ? Find the work done n this time ?

29) ** **The
velocity of a body of mass 5kg reduces from 10 m/s to 5 m/s. What is the change
in momentum of the body? Find Kinetic enegry of both ? Find the work done n this
time ?

30) A 5 kg rifle fires a 10g bullet at a velocity of 500m/s find the recoil velocity of the rifle. Find Kinetic enegry of both ? Find the work done n this time ?

31) A rifle bullet of mass 7 gm leaves the barrel of rifle with a velocity of 300 m/s. If the rifle recoils with a velocity of 1 m/s, find the mass of the rifle Find Kinetic enegry of both ?