Roddick155mph
New User
How fast does one need to hit the ball from the baseline for the ball to go over the fence that is 21 feet away from the opposite baseline. Please give your answer in mph.
tennis ball speed
- Thread starter Roddick155mph
- Start date
phucng_10
Professional
You just have to throw it up and smash it as hard as you can.
teppeiahn1
Rookie
Lol. Hes the next Edison.
Steady Eddy
Legend
Assuming no air resistance, and I aim upward at a 45 degree angle, by the time the ball has gone 100 feet forward, it would be 100 feet high, with no gravity. Gravity pulls it down at the rate of 16 feet per second squared, so if the fence is 20 feet high, it could fall 80 feet and still make it over the fence. So solving for t in 16t^2=80, t = the square root of 5, or about 2.24 seconds. Then figure the horizontal speed. But the racquet is going at a 45 degree angle, so figure it's speed. Let's say about 42 mph.
We've left out air resistance, so you'd have to hit it harder than that. As an estimate, I'd say you have to swing your racquet at nearly 50 mph in order to hit a "home run" and have it go over the opposing fence.
We've left out air resistance, so you'd have to hit it harder than that. As an estimate, I'd say you have to swing your racquet at nearly 50 mph in order to hit a "home run" and have it go over the opposing fence.
Bottle Rocket
Hall of Fame
Are you sure?
CoachingMastery
Professional
Good question, Bottle! Unless gravity has changed since I took physics, the rate of a falling object minus air friciton is 32 feet per second squared.
Bottle Rocket
Hall of Fame
Heh, are you sure about your units? I always thought gravity caused an acceleration.
And either way, I don't know anything about your 16 X 2 business. Most of us would call it 32, rather than listing factors. I don't think Steady Eddy does all his math with numbers that are half the actual.
Last edited:
CoachingMastery
Professional
Yes, that is why it is squared. At the end of two seconds the object will be falling at 64 feet per second and still accerating until it reaches a speed where air friction counters the acceleration factor. (Called "terminal velocity".)
phucng_10
Professional
Actually, it's easier if you round 9.8m/s to 10m/s. I was learning this in Physics last week.
