We know that Different equations of motions are
v = u + at
s = ut + 1/2 at 2
v 2 - u 2 = 2as
u = Initial Velocity
v = Final Velocity
a = Acceleration
t = time taken
s = distance
Now we know that
Acceleration due to gravity for free falling objects is denoted by g
Also Distance (s )in this case becomes height of object (h) from the earth
Hence above equations can be modified as follows
To solve questions, we must remember
If a body is falling downwards
It's initial velocity = u = 0
and acceleration = +g = +9.8 m/s 2
If a body is thrown upwards
It's final velocity = velocity at highest point = 0
and acceleration = -g = -9.8 m/s 2
It's time of ascent = time of decent
Example - If a throw a ball upward and it takes 6 second to come down
Time taken to reach a highest point = 6/2 = 3 seconds
Example 10.2 - A car falls off a ledge and drops to the ground in 0.5 s. Let g = 10 m s–2 (for simplifying the calculations).(i) What is its speed on striking the ground?(ii) What is its average speed during the 0.5 s?(iii) How high is the ledge from the ground?
Example 10.3 - An object is thrown vertically upwards and rises to a heightof 10 m. Calculate (i) the velocity with which the object was thrown upwards & (ii) the time taken by the object to reach the highest point
NCERT Question 13 - A ball is thrown vertically upwards with a velocity of 49 m/s. Calculate(i) the maximum height to which it rises,(ii) the total time it takes to return to the surface of the earth.
NCERT Question 14 - A stone is released from the top of a tower of height 19.6 m.Calculate its final velocity just before touching the ground.
NCERT Question 15 - A stone is thrown vertically upward with an initial velocity of 40 m/s. Taking g = 10 m/s2, find the maximum height reached by the stone. What is the net displacement & total distance covered by the stone?
NCERT Question 17 - A stone is allowed to fall from the top of a tower 100 m high and at the same time another stone is projected vertically upwards from the ground with a velocity of 25 m/s. Calculate when and where the two stones will meet.
NCERT Question 18 - A ball thrown up vertically returns to the thrower after 6 s. Find(a) the velocity with which it was thrown up,(b) the maximum height it reaches, and(c) its position after 4 s.