A pebble of mass 0.05kg is thrown vertically upwards. Give the directi

1.	A pebble of mass 0.05kg 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 momentarily at rest. Do your answer change if the pebble was thrown at an angle of say 45° with the horizontal direction? Ignore air resistance.
Answer» 0.5 N, in a vertically downward direction, in all cases Acceleration due to gravity, irrespective of the direction of motion of an object, always acts downward. The gravitational force is the only force that acts on the pebble in all three cases. Its magnitude is given by Newton's second law of motion as: F = m x a Where, F = Net force m= Mass of the pebble = 0.05 kg a = g = 10 m/s2 ∴F = 0.05 x 10 = 0.5 N The net force on the pebble in all three cases is 0.5 N and this force acts in the downward direction. If the pebble is thrown at an angle of 45° with the horizontal, it will have both the horizontal and vertical components of velocity. At the highest point, only the vertical component of velocity becomes zero. However, the pebble will have the horizontal component of velocity throughout its motion. This component of velocity produces no effect on the net force acting on the pebble. The only force in each case is the force of gravity, (neglecting effects of air) equal to 0.5N vertically downward. The answers do not change, even if the motiodn of the pebble is not along the vertical. The pebble is not at rest at the highest point. It has a constant horizontal component of velocity throughout its motion.

A pebble of mass 0.05kg 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 momentarily at rest. Do your answer change if the pebble was thrown at an angle of say 45° with the horizontal direction? Ignore air resistance.

Answer»

0.5 N, in a vertically downward direction, in all cases

Acceleration due to gravity, irrespective of the direction of motion of an object, always acts downward. The gravitational force is the only force that acts on the pebble in all three cases. Its magnitude is given by Newton's second law of motion as:

F = m x a

Where,

F = Net force

m= Mass of the pebble = 0.05 kg

a = g = 10 m/s2

∴F = 0.05 x 10 = 0.5 N

The net force on the pebble in all three cases is 0.5 N and this force acts in the downward direction.

If the pebble is thrown at an angle of 45° with the horizontal, it will have both the horizontal and vertical components of velocity. At the highest point, only the vertical component of velocity becomes zero. However, the pebble will have the horizontal component of velocity throughout its motion. This component of velocity produces no effect on the net force acting on the pebble.

The only force in each case is the force of gravity, (neglecting effects of air) equal to 0.5N vertically downward. The answers do not change, even if the motiodn of the pebble is not along the vertical. The pebble is not at rest at the highest point. It has a constant horizontal component of velocity throughout its motion.

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