8 A tennis ball machine fires a ball vertically upwards at time
t=0 at 19.6 m/s. Assume that air resistance is negligible and
take g =9.8 m/s
a) Calculate the displacement and velocity of the ball at
t=1.0 s, 2.0 s, 3.0 s and 4.0 s.
b) Use your answers to part a) to draw
i) a graph of displacement against time for the ball
ii) a graph of velocity against time for the ball.

  table and graph are attached

Explanation:

a) The velocity of the ball will be ...

  v(t) = v0 -at

  v(t) = 19.6 -9.8t

The position of the ball will be the integral of this:

  h(t) = ∫v(t)·dt = 19.6t -(1/2)(9.8t^2)

The attached table calculates the vertical position in meters for the required times.

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b) Graphs of displacement (h(t)) and velocity (h'(t)) are shown in the attachment.

he made 11 calls in one day

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 -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [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.