Question

a body of mass 1.5 kg is thrown vertically upward with an initial velocity 30 m/s what will be its potential and kinetic energy at the highest point​

Answer 1

Answer:

To find the potential energy at the end of 2 sec, first we have to find the height which the body attains in 2 sec.

Using the equation, S=ut+1/2 at2

Given,

Initial velocity (u) = 15m/sec, Acceleration (a), g in this question =10, time (t) = 2 sec

So, Height H = 15×2-1/2×10× (2)2

(Acceleration here is -g, because the body is moving upwards)

30-20= 10 m

So, in 2 sec the body will be at the height of 10 m

At this height the potential energy is = mgh

Here, m= mass= 1.5 kg, g=10, H= 10m

So, P.E. = mgh = 1.5×10×10

= 150 Joule

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Answer 2

$\bold{Answer\;:-}$

• Mass of the body, m = 1.5 kg

• Initial velocity through which the body is thrown upwards, u = 30 m/s

• Kinetic energy at the highest point, KE = ½mv²

Therefore, KE = ½*1.5*(0)²

• KE = 0

Now, by using the equation of motion,

• v = u + at

• 0 = 30 + (- 10)(t)

• - 30 = - 10*t

• t = 3 s

Another, equation of motion,

• h = ut + ½gt²

• h = (30)(3) + ½(-10)(3)²

• h = 90 - 45

• h = 45 m

• Potential energy at the highest point, PE = ?

• PE = mgh

• PE = 1.5*(-10)*45

• PE = 675 J

$\bold{Hope\;it \; helps\;!}$