Question

What minimum speed does a 200 g puck need to make it to the top of a frictionless ramp that is 4.1 m long and inclined at 22 ∘?

Answer 1

Answer:

5.5 m/ sec

Explanation:

Because the inclined surface is frictionless so we can assume that total change of energy is zero

i-e ΔE = 0

Or we can say that difference between final and initial energy is zero i-e

Ef- Ei =0

Where,

Ef= final energy at the top of the ramp= KEf+PEf

Ei= Initial energy at the bottom of the ramp=KEi+PEi

So we have

(KEf+PEf)-(KEi+PEi)=0

==>KEf-KEi+PEf-PEi=0            -------------(1)

KEf = mgh = 200×9.8×h

Where h= Sin 22 = h/d= h/4.1

or

0.375×4.1=h

or h= 1.54 m

So, PEf= 200×9.8×1.54=3018.4 j

and KEf= 1/2 m$Vf^{2}$= 0.5×200×0=0 j

PEi= mgh = 200×9.8×0=0 j

KEi= 1/2 m$Vi^{2}$=0.5×200×$Vi^{2}$=100$Vi^{2}$ j

Put these values in eq 1, we get;

0-100 $Vi^{2}$+3018.4-0=0

-100 $Vi^{2}$=-3018.4

==> $Vi^{2}= \frac{3018.4}{100}$ = 30.184

==>  Vi = $\sqrt{30.184} = 5.5 m.sec$