Question

$\huge{ \sf\pink{Question\::-}}$

Give the magnitude and direction of the net force acting on a stone of mass 0.1 kg.

(a) Just after it is dropped from the window of a stationary train,
(b) Just after it is dropped from the window of a train running at a constant velocity of 36 km/h,
(c) Just after it is dropped from the window of a train accelerating with
1 m/s²,
(d) Lying on the floor of a train which is accelerating with 1 m/s², the
stone being at rest relative to the train. Neglect air resistane throughout.


$\huge{ \sf\pink{Content\: Quality\: AnsWer\: needed:-}}$
​

Answer 1

EXPLANATION.

• GIVEN

Stone of mass = 0.1 kg

1) = just after it is dropped from the

window of a stationary train.

=> m = 0.1 kg

=> a = g = 10 m/s²

=> Net force = MA

=> 0.1 X 10 = 1 N

2) Just after it is dropped from the

window of a train running at a constant

velocity of 36 km/h.

=> when the train is running at constant

velocity

=> acceleration will be zero

=> No force acts on on the stone.

3) = Just after it is dropped from the

window of a train accelerating

with 1 m/s².

=> train accelerating with = 1 m/s²

=> F = MA = 0.1 X 1 = 0.1 N acts on the stone

in horizontal direction.

when stone is dropped from the train

force become zero .

net force on stone = 0.1 X 10 = 10 N

acts vertical downward.

4) =Lying on the floor of a train which

is accelerating with 1 m/s², the

stone being at rest relative to the

train. Neglect air resistane throughout.

as stone lying on floor of train so it's

acceleration will be same as train.

=> F = MA = 0.1 X 1 = 0.1 N

Force acting horizontal direction of motion

of train.

Answer 2

[A] 1 Newton, Vertically Downwards.

Explanation ➠

Mass Of The Stone = 0.1 kg.

Acceleration = g = 10 m/s²

As per Newton's 2nd Law,

Force = 0.1 × 10 = 1N.

[B] 1 Newton, Vertically Downwards.

Explanation ➠

When a body moves with constant velocity, its acceleration is zero. So, The net force which is acting on the stone is just because of acceleration due to gravity.

And we know that, it is always vertically downwards.

[C] 1 Newton, Vertically downwards.

Explanation ➠

It is given that,

Acceleration Of Train = 1m/s²

Therefore,

The net force acting on the stone = F = ma = 0.1 × 1 = 0.1 N

Net force acting on the stone is given only by acceleration due to gravity.

So,

F = mg = 1 N

This force acts vertically downwards.

[D] 0.1 Newton, Direction of the train.

Explanation ➠

Acceleration of the train, a = 0.1 m/s²

The net force acting on the stone will be in the direction of motion of the train.

Its magnitude is given by :-

F = ma = 0.1 × 1 = 0.1 N.