Physics Again..

Got this of Trinity Prep Paper for NatSci::: Help!

A golfer driving from the tee swings his club so that the head completes a (virtually) complete
circle in 0.5 s. Make a reasoned estimate of the maximum distance he could hit the ball.

I've tried momentum, energy just can't get the speed of the ball.

T=0.5 sec
estimate r = 1

v=rw (v of club)
w=2pi/T

v (club) = 1 * (2pi/0.5) = 12.6 ms^-1 (1dp)

conservation of momentum (assuming club stops when it hits the ball lol ):

m1v1 = m2v2
v2 = m1v1/m2

estimate mass of club to be 1 kg, ball to be 0.1 kg
m1 = 1
m2 = 0.1

v2 (of ball) = 1*12.6/0.1 = 126 ms^-1

assume he hits it at say 45 degrees

horizontal component (to get time in air) = 126 sin 45 = 88.9 ms^-1

v = u + at
t = (v - u)/a

a = -9.8 ms^-2 (ie 'g')

t = (0 - 88.9)/-9.8 = 9.1 s

therefore distance travelled s = time in air * initial velocity (horizontal component) (assuming no air resistance)

s = 9.1 * (12.6 cos 45) = 80.6 m ie ~80m ?


kinda sounds about right... i dont know much about golf lol. as you need a maximum, id put in bigger mass for weight of club, larger height of club, smaller mass for ball, different angle etc.

i think the method is ok(ish) apart from the cons. of momentum bit, which seems a bit iffy because it assumes all the momentum is transferred to the ball from the club.

Wouldn't you round to 81 m?

Ur suppose to be creative and make assumptions?

ok lets see you do something clever

No, i was asking a question, are u suppose to like assume a club is like 1kg. What happens if u never played golf before?

Thanx, I was using standard velocity equations, using the circumference of a circle, only met this recently in SHM,

Thanks, preparing for interview on wednesday!! lol

oh ok, your question was misleading. yeah, you have to assume values for the necessary variables, otherwise you wouldnt be able to do it

T=0.5 sec
estimate r = 1

v=rw (v of club)
w=2pi/T

v (club) = 1 * (2pi/0.5) = 12.6 ms^-1 (1dp)

conservation of momentum (assuming club stops when it hits the ball lol ):

m1v1 = m2v2
v2 = m1v1/m2

estimate mass of club to be 1 kg, ball to be 0.1 kg
m1 = 1
m2 = 0.1

v2 (of ball) = 1*12.6/0.1 = 126 ms^-1

assume he hits it at say 45 degrees

horizontal component (to get time in air) = 126 sin 45 = 88.9 ms^-1

v = u + at
t = (v - u)/a

a = -9.8 ms^-2 (ie 'g')

t = (0 - 88.9)/-9.8 = 9.1 s

therefore distance travelled s = time in air * initial velocity (horizontal component) (assuming no air resistance)

s = 9.1 * (12.6 cos 45) = 80.6 m ie ~80m ?


kinda sounds about right... i dont know much about golf lol. as you need a maximum, id put in bigger mass for weight of club, larger height of club, smaller mass for ball, different angle etc.

i think the method is ok(ish) apart from the cons. of momentum bit, which seems a bit iffy because it assumes all the momentum is transferred to the ball from the club.

T=0.5 sec
estimate r = 1

v=rw (v of club)
w=2pi/T

v (club) = 1 * (2pi/0.5) = 12.6 ms^-1 (1dp)

conservation of momentum (assuming club stops when it hits the ball lol ):

m1v1 = m2v2
v2 = m1v1/m2

estimate mass of club to be 1 kg, ball to be 0.1 kg
m1 = 1
m2 = 0.1

v2 (of ball) = 1*12.6/0.1 = 126 ms^-1

assume he hits it at say 45 degrees

horizontal component (to get time in air) = 126 sin 45 = 88.9 ms^-1

v = u + at
t = (v - u)/a

a = -9.8 ms^-2 (ie 'g')

t = (0 - 88.9)/-9.8 = 9.1 s

therefore distance travelled s = time in air * initial velocity (horizontal component) (assuming no air resistance)

s = 9.1 * (12.6 cos 45) = 80.6 m ie ~80m ?


kinda sounds about right... i dont know much about golf lol. as you need a maximum, id put in bigger mass for weight of club, larger height of club, smaller mass for ball, different angle etc.

i think the method is ok(ish) apart from the cons. of momentum bit, which seems a bit iffy because it assumes all the momentum is transferred to the ball from the club.

T=0.5 sec
estimate r = 1

v=rw (v of club)
w=2pi/T

v (club) = 1 * (2pi/0.5) = 12.6 ms^-1 (1dp)

conservation of momentum (assuming club stops when it hits the ball lol ):

m1v1 = m2v2
v2 = m1v1/m2

estimate mass of club to be 1 kg, ball to be 0.1 kg
m1 = 1
m2 = 0.1

v2 (of ball) = 1*12.6/0.1 = 126 ms^-1

assume he hits it at say 45 degrees

horizontal component (to get time in air) = 126 sin 45 = 88.9 ms^-1

v = u + at
t = (v - u)/a

a = -9.8 ms^-2 (ie 'g')

t = (0 - 88.9)/-9.8 = 9.1 s

therefore distance travelled s = time in air * initial velocity (horizontal component) (assuming no air resistance)

s = 9.1 * (12.6 cos 45) = 80.6 m ie ~80m ?


kinda sounds about right... i dont know much about golf lol. as you need a maximum, id put in bigger mass for weight of club, larger height of club, smaller mass for ball, different angle etc.

i think the method is ok(ish) apart from the cons. of momentum bit, which seems a bit iffy because it assumes all the momentum is transferred to the ball from the club.

With this amount of uncertainty it would almost be just as good to say "Well, I know that a golfer can hit a ball somewhere around 80m."