Question

A hammer of mass 3 kg falls freely from a height of 45 m. (Assume g = 10 ms) (a) Does the velocity of hammer during the fall depend on the mass of hammer? (b) Calculate the velocity of hammer just before reaching the ground. (c) Calculate the kinetic energy of the hammer just before it​

Answer 1

Answer:

(a) The velocity of hammer during the free fall doesn't depend on the mass of hammer.

(b) The velocity of hammer just before reaching the ground is 30 m/s.

(c) The kinetic energy of the hammer just before hitting the ground is 1350 J.

Explanation:

(a) The acceleration due to gravity is constant (g=10 m/s^2) and didn't depend on the mass of the object.

(b)

Given information:

• Height $h=45 \text{ m}$.
• Initial velocity $u=0\text{ m/s}$ ( falls freely).

The final velocity while hitting the ground can be calculated using the third equation of motion.

$v=\sqrt{u^2+2gh}$

Substituting all known values,

[tex]v=\sqrt{(0\text{ m/s})^2+2\times(10\text{ m/s}^2)\times(45\text{ m})}\\ =30\text {m/s}[/tex]

(c)

Given information:

• Mass of the hammer $m=3\text{ kg}$.
• Velocity just before hitting the ground $v=30 \text{ m/s}$.

The kinetic energy is given as,

$K.E.=\frac{1}{2}mv^2$

Substituting all known values,

[tex]K.E.=\frac{1}{2}\times(3\text{ kg})\times(30 \text{ m/s})^2\\ =1350 \text{ J}[/tex]

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