CBSE-Chapter-MOTION
1.Four
cars A ,B ,C and D are moving on a levelled road. Their distance time graph is
shown as below. The correct statement is
a) Car D is faster than car C
b) Car A is
faster than car D
c)
Car C is slowest
d) Car B is
slowest
2. m/s2
is the SI unit of
a)
Velocity
b) Acceleration
c)
Displacement
d) Speed
3. A bus is moving at a speed of 72 km/h. Its speed is
a)
7.2 m/s
b) 10 m/s
c)
15 m/s
d) 20 m/s
4. An object is moving on a circular path of radius. The
distance and displacement of the object will be when it completes half a circle
a)
Distance 2πr and displacement πr
b) Distance πr and displacement 2r
c)
Both distance and displacement 2r
d) Both
distance and displacement πr
5. Shloka is enjoying on a merry go round which is moving at a
speed of 2m/s. It shows that he is
a) In an accelerated motion
b) In non
accelerated motion
c)
At rest
d) Moving
with uniform velocity
6. The area under speed time graph gives
a)
Displacement
b) Distance
c)
Velocity
d) Average
velocity
7) DEFINE THE FOLLOWING TERMS:
a) SPEED:
Speed is the rate of
change of distance or the distance travelled in unit time.It is a scalar
quantity. The SI unit of speed is ms^-1.
Speed = Distance
travelled / Time taken
b)
VELOCITY:
Velocity is the rate of
change of displacement.It is the displacement in unit time.It is a vector
quantity. The SI unit of velocity is ms^–1.
Velocity = Displacement
/ Time taken
c) ACCELERATION
Acceleration is the
rate of change of velocity or it is the change of velocity in unit time. It is
a vector quantity.The SI unit of acceleration is ms^–2.
Acceleration = Change in velocity/Time
= (Final velocity –
Initial velocity)/Time
A = (v–u)/t
8.
a) WRITE ANY TWO DIFFERENCES BETWEEN
SCALAR AND VECTOR QUANTITIES
Scalar Quantity
|
Vector Quantity
|
Scalar quantity has only magnitude, but no
direction.
|
Vector quantity has both magnitude and direction.
|
Every scalar quantity is one dimensional.
|
Vector quantity can be one, two or three
dimensional.
|
Few
examples of scalar quantity:
|
Few
examples of vector quantity:
|
9)
ABDUL ,WHILE DRIVING TO SCHOOL
,COMPUTES THE AVERAGE SPEED FOR HIS TRIP TO BE 20Km/h. ON HIS RETURN TRIP ALONG
THE SAME ROUTE, THERE IS LESS TRAFFIC AND THE AVERAGE SPEED IS 40 Km/h. WHAT IS
THE AVERAGE SPEED FOR ABDUL’S TRIP?
SOLUTION:
Let the distance
traveled by Abdul from home to school =
s km
Time taken to reach the school
= t1 sec
For Return
journey , Abdul cover distance
= s km
Time = t2 sec
∴ Average speed for forward journey[home
- school ] = Total distance/ Total
time.
20
km/h =
s/t1
∴t1 =
s/20 h --eq(1)
Average speed for
backward journey[school -home] =
Total distance/ Total time.
30 km/h = s/t2
t2 = s/30h ---eq(2)
Average
distance for entire journey =
Total distance/ Total time
=
(s+s)/[s/20 +s/30]
= 2s/s[1/20+1/30]
=
2x20x30/50
= 24 km/hr
10) DERIVE THE FIRST EQUATION OF MOTION
MATHEMATICALLY.
The change in velocity
with time for an uniformly accelerated object. The object starts from the point
D in the graph with velocity, u. Its velocity keeps increasing and after time,
t it reaches the point B on the graph.
Equations of Motion
Time = t = OE = DA
From
the graph we know that, AB = DC
First equation of motion
By definition, Acceleration
=
Change in velocity / Time
=
(Final velocity – Initial velocity)/Time
=
(OC – OD) / OE
=
DC / OE
a
= DC / t
DC
= AB = at
From the graph EB = EA + AB
v
= u + at (1)
This is the first equation of motion
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