Question

Question :-
Find the frictional force on the block as shown in the figure ; if the block is pushed with 15 N force on a rough surface . ( g = 10 m/s )

Answer 1

We are given the following quantities in the question:

• A block being pushed with a force, F = 15 N in forward direction.
• Mass of block, m = 15 kg
• Coefficient of friction, μ = 0.2
• Acceleration due to gravity, g = 10 m/s²

Since Friction is an opposing force hence the frictional force will be in the opposite direction of Force which is in Backward direction.

Let's find the magnitude of friction force,

⇒ f = μN

⇒ f = 0.2 × (mg)

N here, is the Normal force that is the weight of the block which is equal to mass × g

⇒ f = 0.2 (15 × 10)

⇒ f = 2/10 × 15 × 10

⇒ f = 2 × 15

⇒ f = 30 N

Here, we observe that the frictional force is greater than the applied force which means the block would not move due to the frictional friction.

Frictional force on the block is 30 N. Which means one has to apply a force more than 30 N in order to move the block (As per the law of friction, f ≤ μN )

You may think that the net force on the object will be (-30 + 15 = -15 N) which means the block will move backward on applying a force in forward direction, which is impossible in this case.

This is not possible here because Frictional force is a self adjusting force unless the force applied is greater than μN.

The frictional force will be equal to the force applied on the block which cancels out each other. Hence the block remains at rest.

But this is true only when, Force applied ≤ μN.

Answer 2

Answer:

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