Question

20.
i.
ii.
A stone is thrown in a vertically upward direction with a velocity of 5ms- if the acceleration of the
stone during its motion is 10ms in the downward direction.
The time taken by the stone to reach the maximum height is
[ ]
a) 5 s
b) 2.5 s
I
c) 10 s
d) 0.5 s
The speed of the stone after one second later is
[ ]
a) 5 ms' upward
b) 5 ms - downward
c) 2.5 ms upward
d) 2.5 ms -1 downward
The height attained by the stone is
]
a) 2 m
b) 2.5 m
c) 1.25 m
d) 5 m
The displacement of the stone after ane second is
]
a) 5 m
b) 2.5 m
c) 1.25 m
d) zero
SECTION B
iii.
[
iv.

Answer 1

Answer:

Given, initial velocity, u=5ms

−1

Final velocity, v=0

Since, u is upward & a is downward, it is a retarded motion.

∴a=−10ms

−2

Height attained by stone, s=?

Time take to attain height, t=?

(i) Using the relation, v

2

−u

2

=2as, we have

s=v

2

−u

2

/2a

=(0)

2

−(5)

2

/2×(−10)=1.25m

(ii) Using the relation, v=u+at

0=5+(−10)t or

t=5/10=0.5s