Question

solve this question plz​

Answer 1

Question :

A disc of mass 1 kg is kept floating horizontally in air by firing bullets of mass 0.05kg each vertically at it, at the rate of 10 per second. If the bullets rebound with the same speed, the speed with which these are fired will be -

Solution :

❒ As per newton's second law of motion, Force is defined as the rate of change of linear momentum.

Mathematically, F = dp / dt

• We know that momentum is measured as the product of mass and velocity.

So we can say that, F = m (v - u) / dt

★ Bullets rebound with the same speed,

➙ F = m (v - u) / dt

➙ F = m [v - (-v)] / dt

• Negative sign shows opposite direction.

➙ F = 2mv / dt

Force exerted by n bullets...

➙ F = 2nmv / dt

For equilibrium condition of disc,

$\sf:\implies\:F=Mg$

$\sf:\implies\:\dfrac{2nmv}{dt}=Mg$

• n/dt = 10 per second

$\sf:\implies\:2\times 10\times 0.05\times v=1\times 10$

$\sf:\implies\:v=\dfrac{10}{1}$

$:\implies\:\underline{\boxed{\bf{\purple{v=10\:m/s}}}}$

Answer 2

Answer:

hloo again kya 1 baar baat ho skti plz