### Question:

Explain what is meant by uniform circular motion.Give at least three examples.

#### Answer:

Refer to Art. 1.15,Page 35.

### Motion

#### Q 1.

The equation S = ut + ½at^{2} gives information as

(a) velocity is a function of time.

(b) velocity is a function of position.

(c) Position is a function of time.

(d) Position is function of velocity and time.

#### Q 2.

Fill in the blanks :

The rate of change of velocity of a moving body with time is called ______.

#### Q 3.

Are motion and rest absolute or relative? Explain with an example.

#### Q 4.

What do you mean by a body in rest?

#### Q 5.

Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?

#### Q 6.

Which of the following is true for displacement?

(a) It cannot be zero.

(b) Its magnitude is greater than the distance travelled by the object.

#### Q 7.

Fig (below) shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

(a) Which of the three is travelling the fastest?

(b) Are all three ever at the same point on the road?

(c) How far has C travelled when B passes A?

(d) How far has B travelled by the time it passes C?

#### Q 8.

A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.

#### Q 9.

A racing car has a uniform acceleration of 4 m s^{–2}.

What distance will it cover in 10 s after start?

#### Q 10.

What is the average velocity over the “round trip” of an object that is thrown straight up from the ground and falls straight back down to the ground?

#### Q 11.

When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?

#### Q 12.

What does the slope of distance-time graph indicate?

#### Q 13.

Which of the following is true for displacement ?

(a) It cannot be zero.

(b) Its magnitude is greater than the distance travelled by the object.

#### Q 14.

(a)

**Which human virtue was at stake when Archimedes came out with his principle while bathing in a tub** ?

**(b) Briefly discuss three cases where Archimedes Principle is at work**.

#### Q 15.

Distinguish between speed and velocity.

#### Q 16.

Calculate the mass of air enclosed in a room of length,breadth and height equal to 5 m, 3 m and 4 m respectively.Density of air =

$1.3\; Kg/m3$.

#### Q 17.

What is locomotion ?

#### Q 18.

Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.

#### Q 19.

The following is the distancc-time table of a moving car.

(a) Use a graph paper to plot the distance travelled by the car versus the time.

(b) When was the car travelling at the greatest speed ?

(c) What is the average speed of the car ?

(d) What is the speed between 11.25 am and 11-40 am ?

(e) During a part of the journey, the car was forced to slow down to 12 km/h.At what distance did this

*Time* | *Distance* |
---|

10.05 am 10.25 am 10.40 am 10.50 am 11.00 am 11.10 am 11.25 am 11.40 am | 0 km 5 km 12km 22 km 26 km 28 km 38 km 42 km |

#### Q 20.

What is the acceleration of a body moving with uniform velocity ?

#### Q 21.

A metallic sphere of radius 2.0 cm is completely dipped in water.Find the force of buoyancy on it.

#### Q 22.

A body of 2.0 kg floats in a liquid.What is the buoyant force on the body ?

#### Q 23.

A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.

#### Q 24.

A motor cycle moving with a speed of 5 m/s is subjected to an acceleration of 0.2

$m/s2$.Calculate the speed of the motor cycle after 10 second,and the distance travelled in this time.

#### Q 25.

Why do you feel lighter when you swim ?

#### Q 26.

Human corpse always floats on the surface of water,but the head always stays within water.Why ?

#### Q 27.

Is displacement a scalar quantity ?

#### Q 28.

Define the term uniform acceleration.Give one example of uniformly accelerated motion.

#### Q 29.

Using velocity time graph,establish the relation s = ut +

$\frac{1}{2}$$at2$,where the symbols have their usual meanings.

#### Q 30.

A stone tied to one end of a string is rotated in a circle.Explain what happens when the stone is released.

#### Q 31.

Breathing is the process that moves air in (inhaling) and out (exhaling) of the lungs.Breath is life as breathing provides 99% of energy to our bodies.

(a) What happens when we inhale ?

(b)Why a person with pulmonary disease has difficulty in breathing ?What message does it convey ?

(c) What is done to make a newborn have his first breath ?

#### Q 32.

Starting from a stationary position, Rahul paddles his bicycle to attain a velocity of 6 m/s in 30 s.Then he applies brakes such that the velocity of bicycle comes down to 4 m/s in the next 5 s.Calculate the acceleration of the bicycle in both the cases.

#### Q 33.

What remains constant in uniform circular motion ?

#### Q 34.

A body starts from rest.What is zero ?

#### Q 35.

A hydraulic automobile lift is designed to lift cars with a maximum mass of 3000 kg.The area of the piston carrying the load is

$425\; cm2$.What maximum pressure would the smaller piston have to bear ?

#### Q 36.

What is Archimedes’ Principle ? How can it be experimentally verified ?

#### Q 37.

Distinguish between speed and velocity.

#### Q 38.

A bus starting from rest moves with a uniform acceleration of 0.1 ms^{–2} for 2 minutes.

Find (a) the speed acquired, (b) the distance travelled.

#### Q 39.

A scalar quantity has ?

(a) magnitude only

(b) direction only

(c) both direction and magnitude

(d) none of these

#### Q 40.

Ahmed is moving in his car with a velocity of 45 km/h.How much distance will he cover (a) in one minute and (b) in one second ?

#### Q 41.

A body starts to slide over a horizontal surface with an initial velocity of 0-5 m/s. Due to friction, its velocity decreases at the rate of 0.05

$m/s2$.How much time will it take for the body to stop ?

#### Q 42.

What does the slope of a speed-time graph indicate ?

#### Q 43.

Define speed and velocity.What are their SI units ?

#### Q 44.

Using graphical method,derive the equations

v=u+at and s=ut+

$\frac{1}{2}$$at2$ where symbols have their usual meanings.

#### Q 45.

Explain what is meant by uniform circular motion.Give at least three examples.

#### Q 46.

State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.

#### Q 47.

An iron cylinder of radius 14 cm and length 8 cm is found to weigh 369.6 g.Calculate the density of iron.

#### Q 48.

A solid body of mass

$4.0x103$ kg and volume

$2\; m3$ is put in water.Will the body float or sink ?

#### Q 49.

What force acting on an area of

$0.5\; m2$ will produce a pressure of 500 Pa ?

#### Q 50.

A train travels some distance with a speed of 30 km/h and returns with a speed of 45 km/h.Calculate the average speed of the train.