Question

a peddle of mass 0.05 kg is thrown vertically upwards give the direction and magnitude of the net force on the pebble. a) during its upward motion. b) during its downward motion . c) at the highest point where it is momentryly at rest do your answers change if the pebble was thrown at an angle of 45 degree with the horizontal direction ? ignore air resistence.

Answer 1

When an object is thrown vertically upward or it falls vertically downward under gravity then an acceleration g = 10 m/s2s2 acts downward due to the earth’s gravitational pull.
Mass of pebble (m) = 0.05 kg 
(i) During upward motion
Net force acting on pebble (F) = ma = 0.05 X10 N
= 0.50N (vertically downward) 
(ii) During downward motion
Net force acting on pebble (F) = ma = 0.05 X10 N
= 0.50N (vertically downward) 
(iii) At the highest point
Net force acting on pebble
(F) = ma = 0.05 X10N
= 0.50 N (vertically downward) If pebble was thrown at an angle of 45° with the horizontal direction then acceleration acting on it and therefore force acting on it will remain unchanged, i.e., 0.50 N (vertically downward). In case (c), at the highest point the vertical component of velocity will be zero but horizontal component of velocity will not be zero.

Answer 2

The direction and magnitude of the force is always downward and 0.49N

It doesn't change even if the angle is changed.