Question

A stone is dropped from the top of a tower. The stone hits the ground after 5 seconds. Find the height of the tower and the velocity with which the stone hits the ground.





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Answer 1

Explanation:

Correct option is

D

490m

Given,

u=0m/s

g=9.8m/s

2

t=10s

From 2nd equation of motion,

s=ut+

2

1

at

2

h=0×0−

2

1

gt

2

−h=−

2

1

gt

2

h=

2

1

×9.8×10×10

h=490m

Answer 2

Explanation:

Straightforward high school physics homework question.

Assume: the tower is on Earth, and: the stone is released without imparting any initial velocity to it, i.e. it just falls, and: we can neglect air resistance.

s=ut+½at2

s is the distance, which is what we want to find, so the equation is already arranged in the form we need.

u is the initial velocity, which in this case is 0, so the first part of the expression (ut) is 0.

a is the acceleration, which in this case is Earth’s gravitational acceleration, ~9.81 metres per second per second.

t is the time, which we’re given: 5 seconds.

so s=½⋅9.81⋅52=122.625m

The final velocity is given by

v=u+at

We know u is 0, and we have a and t:

v=0+9.81⋅5=49.05ms−1

These equations are part of the equations of motion, also sometimes called the SUVAT equations. If this is a homework question, it will have been already discussed at length in class. It’s worth paying attention, because questions of this nature WILL be part of whatever exam is at the end of it. I did high school physics about 40 years ago, and I can still remember them, and apply them to solving Quora homework questions. Suggest you do the same, if you would rather learn something than just lazily depend on others.