Question

A block of mass 2 kg is placed on the floor a lorry moving horizontally with an acceleration of
8ms". The coefficient of static and kinetic friction between the block and lorry is 0.9 za 0.1
g=10ms the acceleration of the block relative to earth is

Answer 1

Given :

Mass of the block = 2 kg

The horizontal acceleration of the moving lorry = $8 \frac{m}{s^2}$

The coefficient of static friction  between block and lorry = 0.9

Coefficient of kinetic friction between block and lorry = 0.1

To Find :

What is the acceleration of the block relative to the earth ?

Solution :

Since the lorry is moving with acceleration  $8 \frac{m}{s^2}$ , so the Pseudo force on the block will be :

$F_{Pseudo} = m \times a = 2 \times 8 = 16 N$

Now the max friction force on block will be :

$f_{max} =\mu mg$     , here $\mu$ is coefficient of static friction and its value is 0.9 .

       $= 0.9 \times 2 \times 10$

        = 18 N

Here f > F , so  the block will not move relative to lorry .

Hence acceleration of block = $8 \frac{m}{s^2}$

So, the acceleration of block relative to earth is 8 m per second square .

Answer 2

The acceleration of the block relative to earth is 8 m/s²

Given:

Mass of the block = m = 2 kg

Acceleration of the lorry = a = 8 m/s²

Coefficient of static and kinetic friction = μ = 0.9

Acceleration due to gravity = g = 10 m/s²

Explanation:

The force acting on the block due to moving lorry is given by the formula:

f = μ × m × a

On substituting the values, we get,

f = 0.9 × 2 × 10

∴ f = 18 N

The force acting on between block and lorry by the formula:

F = m × a

On substituting the values, we get,

F = 2 × 8

∴ F = 16 N

f > F

Thus, the force acting on the block due to moving lorry is lesser, so, the acceleration of the block relative to earth is 8 m/s².