A ball is thrown vertically upward from the top of a tower 40m high with velocity 10m/sec find time when it strikes ground

Explanation:

Displacement ⇒ -40 m (the ball strikes the ground)

Initial velocity ⇒ 10 m/s

Acceleration of gravity ⇒ -10 m/s² (upward acceleration)

We can use a formula to find the time taken.

Plugging in the values.

Solve for .

Factor the quadratic expression.

Set the factors equal to 0.

t = -2 and t = 4 (time value will not be negative in this case)

The time the ball takes to strike the ground is 4 seconds.

Find time when it strikes ground.

s = ut + 1/2 at²

We will first calculate the time taken by the ball to reach the highest point by using the formula:

S = ut + 1/2 at²

★ Substituting the values in the above formula,we get:

⇒ -40 = 10 × t + 1/2 × -10 × t²

⇒ -40 = 10t + ( - 5 ) × t²

⇒ -40 = 10t - 5 t²

⇒ 5t² - 10t - 40

⇒ 5t² - 20t + 10t - 40

⇒ 5t ( t - 4 ) + 10 ( t - 4 )

⇒ t - 4 = 0 and 5t + 10 = 0

⇒ t = 4 and t = -2

Thus,time taken is 4 seconds. [ Ignore negative number. ]

air exerts forces on falling objects near earth’s surface.

explanation:

the term 'free falls' refer to object that are falling towards the earth, in a situation in which gravity is the only force acting on the object.

for an object in free fall, the acceleration is constant (g, the gravitational acceleration), and so the velocity of the object constantly increases.

for objects near earth's surface, there is always another force acting on the object: the resistance due to the air. this force is opposed to the direction of fall of the object, and it is proportional to the velocity of the object, so as the object falls down, this force increases up to a point when it balances the force of gravity, and the object continues its motion at constant velocity (called terminal velocity). since in this case gravity is not the only force acting on the object, we are not in a situation of free fall.