Finding the magnitude of velocity vector

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To find the magnitude of the velocity vector for a cricketer throwing a 147g ball with a force of 7.5N for 0.84s at a 39-degree angle, the acceleration is calculated as 51.02 m/s², leading to a velocity of 42.86 m/s. The equation for range involves determining the horizontal and vertical components of this velocity using trigonometry. The horizontal range is calculated as 225.52m, based on the displacement formula s=vt. The discussion raises questions about the applicability of the range equation, particularly regarding displacement in the y-axis. Understanding these calculations is essential for accurately determining the ball's trajectory.
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Homework Statement


A cricketer throws a 147g ball by exerting a force of 7.5N for 0.84s. If the launch angle is 39 degrees from horizontal, calculate the range of the ball.

Homework Equations

The Attempt at a Solution


I have the range equation and I just need to find the magnitude of the velocity vector but I'm not sure how I'd find that with the given quantities?
 
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What is the answer given in solutions section?
 
Day3091 said:

Homework Statement


A cricketer throws a 147g ball by exerting a force of 7.5N for 0.84s. If the launch angle is 39 degrees from horizontal, calculate the range of the ball.

Homework Equations

The Attempt at a Solution


I have the range equation and I just need to find the magnitude of the velocity vector but I'm not sure how I'd find that with the given quantities?
Can you determine the acceleration ?
 
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I thought it was a=f/m = 51.02m/s^2 and then v=at for 42.86 ms^-1 I was going to use a particular formula for range

The solution in the back of the mock exam says f=ma rearranged for m x deltav/deltat

Which is then rearranged for deltav = Fdeltat / m = 42.8 ms

Trigonometry to then find the Vx and Vy components which can then be plugged into t = v-u/a giving us a time value. This completes the vertical plane suvat.

Horizontal 'range' was simply given as displacement s=vt: 42.8(cos39) x 6.78 = 225.52m

upload_2017-6-9_20-58-45.png

When would this equation for range be applicable? It's defined as 'the displacement in the x-axis when the y-axis displacement is 0.' I imagine there is still some displacement for this scenario even though it doesn't end in the y axis? Making this equation irrelevant?
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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