Question

an object is thrown vertically upwards and rises to a height of 20 m. calculate
i.) the velocity with which the object was thrown upwards,
ii.) the time taken by the object to reach the highest point
(g= 10 m/s^-2)
for class 9th chapter gravitation

Answer 1

v^2=u^2+2as
s=20m
v=0m/s
a=10m/s^2
u=20m/s(1 ans)

v=u+at
0=20+10t
t=2 sec
for

Answer 2

Given that,

Distance traveled by an object, s = 20 m

Let the final speed of the object, v = 0

To find,

(A) The velocity with which the object was thrown upwards.

(B) The time taken by the object to reach the highest point.

Solution,

(A) Let u is the velocity with which the object was thrown upward. Using third equation of motion as :

$v^2-u^2=2as$

Here, a = -g and v = 0

$-u^2=-2gs\\\\u=\sqrt{2gs} \\\\u=\sqrt{2\times 10\times 20} \\\\u=20\ m$

(B) Let t is the time taken by the object to reach the highest point. So,

$v=u-gt\\\\u=gt\\\\t=\dfrac{u}{g}\\\\t=\dfrac{20}{10}\\\\t=2\ s$

Hence, this is the required solution.

Learn more,

Kinematics

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