Question:
Consider the following two scenarios and tell in which case average speed is harmonic mean or arithmetic mean?
Case 1: A fellow travels from city A to city B. For the first hour, he drove at the constant speed of 20 km/hr. Then he (instantaneously) increased his speed and, for the next hour, kept it at 30 km per hour. Find the average speed of the motion.
Case 2: A fellow travels from city A to city B. The first half of the way, he drove at the constant speed of 20 km per hour. Then he (instantaneously) increased his speed and traveled the remaining distance at 30 km per hour. Find the average speed of the motion.
Answer:
Case 1: Arithmetic mean i.e. avg speed = (20 + 30)/2 = 25 km/hr
Case 2: Harmonic mean i.e. avg speed = 2/(1/20 + 1/30) = 24 km/hr
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.
When will you say a body is in (i) uniform acceleration? (ii) nonuniform acceleration?
Q 16.
What is locomotion ?
Q 17.
(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 18.
Derive graphically the equation of motion for position-velocity relation of a body moving with uniform acceleration.
Q 19.
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 20.
What is the acceleration of a body moving with uniform velocity ?
Q 21.
Why do you feel lighter when you swim ?
Q 22.
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 23.
Using velocity time graph,establish the relation s = ut +
,where the symbols have their usual meanings.
Q 24.
What is Archimedes’ Principle ? How can it be experimentally verified ?
Q 25.
A particle is moving in a circle of diameter 5 m. Calculate the distance covered and the displacement when it completes 3 revolutions.
Q 26.
Is displacement a scalar quantity ?
Q 27.
Define the term uniform acceleration.Give one example of uniformly accelerated motion.
Q 28.
A metallic sphere of radius 2.0 cm is completely dipped in water.Find the force of buoyancy on it.
Q 29.
A body of 2.0 kg floats in a liquid.What is the buoyant force on the body ?
Q 30.
Human corpse always floats on the surface of water,but the head always stays within water.Why ?
Q 31.
A scalar quantity has ?
(a) magnitude only
(b) direction only
(c) both direction and magnitude
(d) none of these
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 does the slope of a speed-time graph indicate ?
Q 34.
Explain what is meant by uniform circular motion.Give at least three examples.
Q 35.
State velocity-time relation in uniformly accelerated motion. Use graphical method to obtain this relation.
Q 36.
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 37.
A solid body of mass
kg and volume
is put in water.Will the body float or sink ?
Q 38.
What force acting on an area of
will produce a pressure of 500 Pa ?
Q 39.
What is meant by scalars and vectors?
Q 40.
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 41.
A body starts from rest.What is zero ?
Q 42.
Convert a speed of 15 m/s into km/h
Q 43.
A stone tied to one end of a string is rotated in a circle.Explain what happens when the stone is released.
Q 44.
Using graphical method,derive the equations
v=u+at and s=ut+
where symbols have their usual meanings.
Q 45.
An iron cylinder of radius 14 cm and length 8 cm is found to weigh 369.6 g.Calculate the density of iron.
Q 46.
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 47.
Why do objects float or sink when placed on the surface of a liquid ?
Q 48.
Distinguish between speed and velocity.
Q 49.
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 50.
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 ?
