10 numerical form chapter motion
Answers
Question 1
A train accelerates from 36 km/h to 54 km/h in 10 sec.
(i) Acceleration
(ii) The distance travelled by car.
Answer a. Acceleration is given by
a
=
Δ
v
Δ
t
Δ
v
=
54
−
36
=
18
k
m
/
h
r
=
5
m
/
s
So a=.5 m/s2
b. Distance is given by
S
=
u
t
+
1
2
a
t
2
So s=125m
Question 2
A body whose speed is constant
(a) Must be accelerated
(b) Might be accelerated
(c) Has a constant velocity
(d) Cannot be accelerated.
Answer = might be accelerated
Question 3
A truck travelling at 54 km/h is slow down to 36 km/h in 10 sec. Find the retardation
Answer Acceleration is given by
a
=
Δ
v
Δ
t
So a=-.5 m/s2
Negative sign implies retardation
Question 4
A particle is moving in a circle of diameter 20 m. What is its distance and as per the table given below
Rounds Displacement Distance
1
1.5
2
2.5 Answer
Rounds Displacement Distance
1 0
20
π
1.5 20 m
30
π
2 0
40
π
2.5 20m
50
π
Question 5
A scooter travelling at 10 m/s speed up to 20 m/s in 4 sec. Find the acceleration of scooter.
Answer Acceleration is given by
a
=
Δ
v
Δ
t
So a=2.5 m/s2
Question 6
A train starts from rest and accelerate uniformly at the rate of 5 m/s2 for 5 sec. Calculate the velocity of train in 5 sec.
Answer 25m/s
Question 7
A object moves with uniform positive acceleration. Its velocity-time graph will be
(a) A straight line parallel to the time axis
(b) A straight line inclined at an obtuse angle to the time axis
(c) A straight line inclined at an acute angle to the time axis
(d) None of these.
Answer Answer is (c)
Question 8
The maximum speed of a train is 90 km/h. It takes 10 hours to cover a distance of 500 km. Find the ratio of its average speed to maximum speed?
Answer Average speed=500/10=50 km/hr
Ratio of average speed to maximum speed= 50:90=5:9
Question 9
A car start from rest and acquire a velocity of 54 km/h in 2 sec. Find
(i) the acceleration
(ii) distance travelled by car assume motion of car is uniform?
Answer a) Acceleration is given by
a
=
Δ
v
Δ
t
So a=7.5 m/s2
b) Distance is given by
S
=
u
t
+
1
2
a
t
2
and can be calculated using the above formula.
and answer is 15m
Question 10
An object dropped from a cliff falls with a constant acceleration of 10 m/s2. Find its speed 5 s after it was dropped.
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