**Answer:**

Option C : 290 J

**Explanation:**

We can use conservation of energy to estimate the kinetic energy when the object hits the ground:

When the object is at its initial height of 15 meters, it velocity is zero (falls from this position), therefore the total energy it possesses is due to potential energy given by the expression:

Joules

At the moment the object hits the ground from its free fall, its potential energy is zero, while its kinetic energy must equal the rest. So at that moment the object's kinetic energy must be 294 Joules.

<span>Heat energy is transferred from warmer objects to cooler objects.

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**Answer:**

**Explanation:**

**The centripetal force experienced by the steel toolbox is provided by the friction between the toolbox and the bed of the truck.**

**Therefore,**

--------------------------------(1)

**Here,**

v - speed of truck

m - mass of toolbox

r - radius of curve around which the truck is turning

f - frictional force

μmg

**In order to obtain Vmax, frictional force must also be max**

Thus,

f = μmg--------------------------------------------------(2)

**Substitute (2) in (1)**

μmg

μgr

g - 9.8 m/

**The standard value of coefficient of static friction between steel and steel is **

**μ ≈ 0.7**

Therefore,

d=18cm=0.18m thickness of board

vi=420m/s speed before entering the board

vf=320m/s speed when leaving the board

vf²=vi²+2×a×d

Acceleration a=(vf²-vi²)/2/d

a=-205.5m/s².

As expected, a is negative because the bullet is decelerated.

vf=vi+a×t

t=(vf-vi)/a=(320-420)/(-205.5)= 100/205.5=0.486s

t=0.486s=486ms

**Answer:**

2.61

**Explanation:**

91.44/35=2.61257142857 or 2.61