Question:
A driver of a car travelling at 52 km/h applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km/h in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
Answer:
Car A: Initial speed (uA) = 52km/h = 52 x 1000/3600 = 14.4 m/s
Final Speed (vA) = 0 m/s
Time taken (tA) = 5s
Car B: Initial speed (uB) = 3km/h = 3 x 1000/3600 = 0.83 m/s
Final Speed (vB) = 0 m/s
Time taken (tB) = 10s
The speed-time graph will look like:
Distance covered by car A = Area of △ AOB = ½ x AO x OB = ½ x 14.4 x 5 = 36m
Distance covered by car B = Area of △XOY = ½ x OX x OY = ½ x 0.83 x 10 = 4.15 m
⇒ Car A covers more distance as compared to car B.
Motion
Q 1.
The equation S = ut + ½at2 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.
What does the slope of distance-time graph indicate?
Q 12.
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 13.
Distinguish between speed and velocity.
Q 14.
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 =
.
Q 15.
(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 16.
What is locomotion ?
Q 17.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 18.
What is the acceleration of a body moving with uniform velocity ?
Q 19.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 20.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
Q 21.
A motor cycle moving with a speed of 5 m/s is subjected to an acceleration of 0.2
.Calculate the speed of the motor cycle after 10 second,and the distance travelled in this time.
Q 22.
Is displacement a scalar quantity ?
Q 23.
Explain what is meant by uniform circular motion.Give at least three examples.
Q 24.
Why do you feel lighter when you swim ?
Q 25.
Human corpse always floats on the surface of water,but the head always stays within water.Why ?
Q 26.
What does the slope of a speed-time graph indicate ?
Q 27.
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
.What maximum pressure would the smaller piston have to bear ?
Q 28.
A metallic sphere of radius 2.0 cm is completely dipped in water.Find the force of buoyancy on it.
Q 29.
What force acting on an area of
will produce a pressure of 500 Pa ?
Q 30.
Why do objects float or sink when placed on the surface of a liquid ?
Q 31.
What is Archimedes’ Principle ? How can it be experimentally verified ?
Q 32.
A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.
Q 33.
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.
Q 34.
A body starts from rest.What is zero ?
Q 35.
A body of 2.0 kg floats in a liquid.What is the buoyant force on the body ?
Q 36.
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 37.
What is meant by scalars and vectors?
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.
What is the SI unit of acceleration ?
Q 40.
Convert a speed of 15 m/s into km/h
Q 41.
Define the term uniform acceleration.Give one example of uniformly accelerated motion.
Q 42.
Using velocity time graph,establish the relation s = ut +
,where the symbols have their usual meanings.
Q 43.
State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.
Q 44.
An iron cylinder of radius 14 cm and length 8 cm is found to weigh 369.6 g.Calculate the density of iron.
Q 45.
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 46.
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
.How much time will it take for the body to stop ?
Q 47.
Explain the terms : uniform motion and non-uniform motion with examples.
Q 48.
The mass of a solid rectangular block of iron is 23.6 g and its dimensions are 2.1 cm x 1.2 cm x 1.1 cm.Calculate the density of iron.
Q 49.
A solid body of mass
kg and volume
is put in water.Will the body float or sink ?
Q 50.
Define thrust What is its unit ?
