Physics, 21.09.2019 17:10 Nycin

Aball is thrown vertically upward, which is the positive direction. a little later it returns to its point of release. the ball is in the air for a total time of 8.00 s. what is its initial velocity? neglect air resistance.

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Final Velocity = Vf = 0 m/s > (Vf = 0 because ball's speed at its max height is 0) Initial Velocity = Vi = ? Total time (upward & downward) = 8.0 seconds * Time upward = 4 seconds & ( As time for ball upward & downward is equal ) * Time downward = 4 seconds.. Gravitational Acceleration = g = -9.8 m/sÂ˛ Use Equation; Vf = Vi - gt 0 = Vi - 9.8 * 4 0 = Vi - 39.2 39.2 = Vi => Vi = Initial Velocity = 39.2 m/s

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force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

$f\alpha \frac{dp}{dt}$

⇒ $f= k \frac{dp}{dt}$

here k is the proportionality constant whose value is 1.

$f=\frac{dp}{dt}$

$f= \frac{d[mv]}{dt}$

$f= m\frac{dv}{dt} +v\frac{dm}{dt}$

$f=ma+v\frac{dm}{dt}$ [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.

Answer from: Quest

Because its reliable. there is no pollution the chances of a radiation leak is low

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