A catapult used to hold a stone of mass 500g is extended by 20cm with an applied force F. If the stone leaves with a velocity of 40m/s, the value of F is

Ajnnamchi

5 years ago

Since the stone is moving, it is experiencing Kinetic energy and K.E=1/2MV2.
Also recall that Work done by an elastic material is 1/2FE.
Since work done is always equal to energy therefore
Work done by elastic material=K.E of the moving stone.
Therefore
1/2FE = 1/2KE2.
So the halves in both sides will cancel themselves, then what you will have remaining is FE=MV².
Make F subject of the formula.
Then F=(MV²)/E.
M=500g=0.5kg
E= 20cm=0.2m
V=40m/s.
Therefore substituting the values into the equation.
F=(0.5×40×40)÷0.2
F=4000N= 4×10³N.
So myschool is correct

tyjesma

11 years ago

E.P.E=K.E....½Fe=½Mv²....F=?, e=20cm/100---»0.2, M=500g/1000----»0.5, V²=40 x 40---»1600....½ x F x 0.2= ½ x 0.5 x 1600 -----»0.1F=400, F=400/0.1=4000N Or 4 x 10³N

topaz16

9 years ago

v^2=u^2+2as

s=20cm=0.2m

40x40=0+2x0.2xa



1600/0.4=a

a=4000



f=ma

m=500g..0.5kg

f=0.5x4000

f=2000N=2x10^3N

Jaetrill

12 years ago

M= 500g = 0.5kg, v = 40m/s,

e= 20cm = 0.2m, w=?, F=?



W = 1/2mv^2

w= 1/2*0.5 * 40^2

w = 0.25 * 1600

w = 400J



w =1/2Fe

400 = 1/2 * F * 0.2

1/2F = 400/0.2

1/2F = 2000

F = 2000 * 2

F = 4000N

F = 4 * 10^3N

ans = C

Ibnhamzaht

6 years ago

Energy stored in extended catapult = Kinetic energy gained by the stone

⇒1/2Fe = 1/2mv²
F = mv²/e
= (0.5 x 40²)/0.2
= 4000
= 4 x 10³ N

samtony12

10 years ago

1/2mv2 equals 1/2fe

Tprince443

7 years ago

The correct answer is option C

Ayemhenre Joshua

2 months ago

what I understand about intense Examination like Jamb, you need to manipulate shortcuts to find a way very fast, not using normal route, you will only end up wasting time. Like this question, I just converted the cm to m and multiply all through to get the answer, no time. 0.5*500*40=4000 which is equal to 4*10^3

Psyrhin

1 year ago

myschool please correct your options it's meant to be B not C.
Even the tutorial video says B.
Thank you

chizee7703

6 years ago

It's supposed to be C using 1/2mv2=1/2Fe

Shegzylizzy

2 years ago

Hi

nwaohadivine

5 years ago

I agree with you 💯

tuny44ril

4 years ago

the answer is C not A f=4.0*10^3N

kakakakakaka

1 year ago

i taught 1/2*F*e = 1/2*m*v^2 =1/2*K*e^2
but you people used workdone = force*distance
when we have extension there .
i think the appropiatre formular to use is that of 1/2Force*extension

Sensei

2 months ago

bonus question 😒