- #1
nysnacc
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Homework Statement
Homework Equations
∑Fav = mv2 - mv1
The Attempt at a Solution
We have to separate v in x dir and y dir?
Average force exerted on the ball
- Thread starter nysnacc
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- Average Average force Ball Force
In summary, the problem involves finding the average total force and the force exerted by the foot on a ball, given its initial and final velocities. The weight of the ball must be considered in the calculation of the total force, but not in the force exerted by the foot. The weight should be subtracted from the force of the kick, and the direction of the forces must be taken into account as they are vectors. The correct values for the forces are 45 N and 48.87 N for the average total force and the force exerted by the foot, respectively.
∑Fav = mv2 - mv1
We have to separate v in x dir and y dir?
- #2
Doc Al
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Why? (Note that it starts from rest.)nysnacc said:
- #3
nysnacc
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but are part one and part two asking the same thing?
- #4
Doc Al
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No. One asks for the average total force on the ball. The other part asks for just the force exerted by the foot.nysnacc said:
- #5
nysnacc
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For the average total force on the ball (1st part). what equation should i use?
For the (2nd part) force exerted by the foot, the equation is F = (mv2- mv1 ) / Δt
For the (2nd part) force exerted by the foot, the equation is F = (mv2- mv1 ) / Δt
- #6
Doc Al
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No, that will give the average total force on the ball.nysnacc said:
- #7
nysnacc
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That's total force exerted on the ball?
- #8
nysnacc
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For part 1,
F = 1/ Δt * ∫ F dt ?? which is (mv2- mv1 ) / Δt ??
For part 2,
F = (mv2- mv1 ) / Δt - mg (cuz the question said subtract the weight)
F = 1/ Δt * ∫ F dt ?? which is (mv2- mv1 ) / Δt ??
For part 2,
F = (mv2- mv1 ) / Δt - mg (cuz the question said subtract the weight)
- #9
Doc Al
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Yep.nysnacc said:
- #10
Doc Al
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Yes.nysnacc said:
Careful. Forces are vectors, so here you need to consider the directions of each.nysnacc said:
- #11
nysnacc
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For part 2
(mv2- mv1 ) / Δt (going up)
mg (going down)
what should i do with the 60 deg which is given?
(mv2- mv1 ) / Δt (going up)
mg (going down)
what should i do with the 60 deg which is given?
- #12
Doc Al
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That's the direction of the average total force on the ball.nysnacc said:
- #13
nysnacc
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Part 1, F = 45 N
Part 2 F = 41.236 N?
Part 2 F = 41.236 N?
- #14
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I'm not sure whether the hint given in the question is simply wrong or is assuming the weight, being a downward force, will be expressed as a negative quantity. Ask yourself this: does the presence of gravity increase or reduce the force needed from the boot to achieve the given velocity?nysnacc said:
Secondly, forces are vectors. You cannot add (or subtract) forces acting in different directions by adding their magnitudes.
- #15
nysnacc
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Is #1 correct, 45 N
- #16
nysnacc
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#2 i have F = Fav (cos i + sin j) + mg (-j)
= (Fav cos )i + ( Fav sin - mg ) j
= (Fav cos )i + ( Fav sin - mg ) j
- #17
Doc Al
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Yes.nysnacc said:
- #18
nysnacc
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why is my #2 not correct?Doc Al said:
- #19
Doc Al
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You made a mistake with the sign of the weight vector.nysnacc said:
- #20
nysnacc
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Fav - mg (-j) ??
so it is a plus?
so it is a plus?
- #21
nysnacc
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So 48.87 N?
#2 is greater than #1
#2 is greater than #1
- #22
Doc Al
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##\vec{F_{total}} = \vec{F_{kick}} + \vec{F_{weight}}##
To find the force of the kick you must subtract the weight vector, but the weight points down.
To find the force of the kick you must subtract the weight vector, but the weight points down.
- #23
Doc Al
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Yes.nysnacc said:
FAQ: Average force exerted on the ball
What is the definition of average force exerted on the ball?
The average force exerted on the ball is the overall force applied to the ball over a given period of time, divided by the duration of that time period. It is a measure of the average impact or push on the ball.
How is average force exerted on the ball calculated?
The average force exerted on the ball is calculated by dividing the total force applied to the ball by the duration of time in which the force was applied. This can be expressed as the equation F = m x a, where F is the force, m is the mass of the ball, and a is the acceleration.
What factors affect the average force exerted on the ball?
The average force exerted on the ball is affected by several factors, including the mass and velocity of the ball, the surface it is being pushed on, and the duration of time in which the force is applied. Other factors such as air resistance and friction can also play a role.
Why is it important to calculate the average force exerted on the ball?
Calculating the average force exerted on the ball is important for understanding the impact or push that the ball experiences. It can also help in analyzing the efficiency and effectiveness of a particular force or technique used to move the ball.
How can the average force exerted on the ball be measured?
The average force exerted on the ball can be measured using a force sensor or a force plate, which can accurately measure the force applied to an object. In some cases, it can also be estimated by analyzing the motion of the ball and using equations such as Newton's Second Law.