A ball is dropped from rest from the top of a building. What force is responsible for the downward motion of the ball?

the force of gravity
the force of tension
the normal force
the pushing force

Force of gravity

Explanation:

A ball is dropped from rest from the top of a building. The forces acting on the ball at this position are : force of gravity and air resistance.

The air drag can be neglected as for air it is less. We can say that force of gravity is the only force that is responsible for the downward motion of the ball.

Hence, the correct option is (A). "force of gravity".

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answer: at 24 february, 2014 the population gets twice of its initial population.

explanation:

since we have given that

the population for alpha city, t years after january 1, 2004 is given as

first we find out the initial population, i.e. t=0,

so, our quadratic equation becomes,

according to question, we have said that if the population has twice its initial population, then it becomes

so, time taken to reach this above mentioned population is given by

now, we know that time can't be negative so, we take t=9.149 years.

hence, at 24 february, 2014 the population gets twice of its initial population.