MHB Work energy principle and power

[Shah 72]

A golf ball of mass 45.9g is hit from a tee with speed 180km/ h. The ball rises to a height of 20m having traveled along a curved path of length 61.875m. At the highest point of its path the ball is traveling at 144 km/h
a) Find the magnitude of the avg resistance force acting on the golf ball.
I got the and resistance =0.2N

The ball travels a further 105.8m along a curved path to land on the green. The green is 4m lower than the tee. The average resistance remains unchanged
b) find the speed of the ball just before it lands on the green
I got the ans v= 35m/s

The ball is traveling vertically when it lands on the green, where it is immediately brought to rest.
C) show that the energy absorbed by the green is 30.3J
I don't know how to work this out. Pls help

 

[topsquark]

I don't know how to work this out. Pls help

You don't know how to work what part out? Again, we can't really help you until we know what you are having troubles with! You have posted a number of problems without showing us anything about what you don't know. This has to end.

Let's start from the beginning. This problem is going to involve the work-energy theorem. You have been shown the form of this equation several times here so please start by telling us what the equation is and what your question is.

-Dan

 

[Shah 72]

You don't know how to work what part out? Again, we can't really help you until we know what you are having troubles with! You have posted a number of problems without showing us anything about what you don't know. This has to end.

Let's start from the beginning. This problem is going to involve the work-energy theorem. You have been shown the form of this equation several times here so please start by telling us what the equation is and what your question is.

-Dan

It's question c iam not able to solve

 

[topsquark]

It's question c iam not able to solve

Since the ball didn't bounce (and we technically don't have to assume that) the green absorbed all the kinetic energy that the ball had when it landed. So that would be...

I ran through the whole problem and you are not off by much. I suspect that you are not carrying enough decimal places when you are rounding. Keep 5 or so significant digits. I got 0.1884 N for part a, 33.888 m/s for part b, and 26.356 J for part c. I couldn't replicate your results so I don't know where you might be off.

-Dan

 

[Shah 72]

Ok

Since the ball didn't bounce (and we technically don't have to assume that) the green absorbed all the kinetic energy that the ball had when it landed. So that would be...

I ran through the whole problem and you are not off by much. I suspect that you are not carrying enough decimal places when you are rounding. Keep 5 or so significant digits. I got 0.1884 N for part a, 33.888 m/s for part b, and 26.356 J for part c. I couldn't replicate your results so I don't know where you might be off.

-Dan

Thank you so much for replying.
According to textbook the ans in 0.2N for q(a)
So for q(a)
m= 0.0459kg, u= 50m/s, h=20m, s=61.875m, highest point v=40m/s
So Increase in KE= 1/2mv^2- 1/2mu^2=-20.655J
Increase in GPE= mgh=9.18J
Work done against resistance = -F×S=-61.875F
So I get F= 0.2N as given in the textbook
For (b) s=105.8, h= 20-4= 16m, u=50m/s
Increase in KE=0.02295v^2-57.375J
Increase in GPE= 7.344J
Work done against resistance =-21.16J
So I get v=35.4m/s, as mentioned in the textbook I rounded it to 35 m/s.
I don't understand how to calculate q(c). I don't know what components to consider.

 

[Shah 72]

I

Since the ball didn't bounce (and we technically don't have to assume that) the green absorbed all the kinetic energy that the ball had when it landed. So that would be...

I ran through the whole problem and you are not off by much. I suspect that you are not carrying enough decimal places when you are rounding. Keep 5 or so significant digits. I got 0.1884 N for part a, 33.888 m/s for part b, and 26.356 J for part c. I couldn't replicate your results so I don't know where you might be off.

-Dan

If I consider the final KE the ball lands = -28.11J
Final GPE= -1.836 J by taking h=4m
Work done against resistance = -0.2×4=-0.8J
So total will be 30.7. I don't get 30.3J .is this OK?

 

[Shah 72]

Since the ball didn't bounce (and we technically don't have to assume that) the green absorbed all the kinetic energy that the ball had when it landed. So that would be...

I ran through the whole problem and you are not off by much. I suspect that you are not carrying enough decimal places when you are rounding. Keep 5 or so significant digits. I got 0.1884 N for part a, 33.888 m/s for part b, and 26.356 J for part c. I couldn't replicate your results so I don't know where you might be off.

-Dan

Can you pls pls explain an easy method how to calculate the energy gained by the green when the ball falls. If I get the concept right, I can calculate with similar problems. Iam not understanding which energy to take whether it's initial energy or its the final energy when the ball hits the green. Pls

 

[topsquark]

I'm not sure what you are asking for. The best I can come up with is to say that if the ball lands and does not bounce then all of it's kinetic energy is absorbed by the green. That's simply a matter of energy conservation.

-Dan

 

[Shah 72]

I'm not sure what you are asking for. The best I can come up with is to say that if the ball lands and does not bounce then all of it's kinetic energy is absorbed by the green. That's simply a matter of energy conservation.

-Dan

Ok got it. Thank you so much!