Question

A 1.2-kg mass is projected from ground level with a velocity of 31.3 m/s at some unknown angle above the horizontal. A short time after being projected, the mass barely clears a 16-m tall fence. Disregard air resistance and assume the ground is level. What is the kinetic energy of the mass as it clears the fence

Answer 1

The kinetic energy will be "399.65 J".

Step-by-step explanation:

Given:

Mass,

m = 1.2 kg

Velocity,

v = 31.3 m/s

The total energy of mass will be:

⇒
`E=K+U`

or,

⇒
`E=.5mv^2+mgh`

By putting the values, we get

`=.5(1.2)(31.3)^2+0`

`=0.6* 979.69+0`

`=587.81 \ J`

Since,

The system's total energy is unchanged, then

⇒
`E=K+U`

or,

⇒
`E=K+mgh`

`587.81=K+1.2(9.8)(16)`

`587.81=K+188.16`

`K=587.81-188.16`

`=399.65 \ J`