Force and momentum : Force and momentum Newton’s Laws Of Motion
Review: : Review: Momentum: quantity of movement of and object
Formula to calculate momentum: P = m*v
where:
P : momentum
m : mass
v : velocity of the moving object
Acceleration: rate of change of velocigy
Formula to calculate acceleration: a = ( vf – vi ) / ?t
where:
a : acceleration
Vf : final velocity; ?t = change in time
Vi : initial velocity
Review: : Review: Force: a push or a pull
Formula to calculate force: F = m*a
where:
F : net force
m: mass
a: acceleration
What is the relationship between Force and Momentum: : What is the relationship between Force and Momentum: To find the relationship between Force and Momentum let’s
Consider that F = m * a
Substitute a = ( vf – vi ) / ?t in F = m * a. Use the distributive property to find the product.
Since Vf and Vi are just velocities of an object at different times, and since P = m * v , lets substitue all the m * v terms that we have in the equation we got in step #2 with P , which is equal to m*v. Identify with the adequate subscript, “f” for final, or “i” for initial each of the P ‘s.
Conclusions: : Conclusions: Force = ( Pf – Pi ) / ?t
Force is equal to change of momentum in time
F = ?P / ?t
Now, we will learn a new concept. To find out what this new concept is, let’s multiply both sides of the equation F = ?P / ?t by ?t .
Conclusions: : Conclusions: F * ?t = ?P
This means that the change of momentum in and object is the result of applying a force to an object for a certain amount of time. So now we have arrived to a new concept:
Impulse is a vector quantity, represented by the leetter J defined as the product of the force acting on a body and the time interval during which the force is excerted.
J = F * ?t
Now, look at this last equation and find the units of impulse.
Practice Problems: : Practice Problems: A soccer player kicks a 0.1 kg ball that is initially at rest so that it moves with a velocity of 20 m/s.
What is the impulse the player imparts to the ball?
If the player’s foot was in contact with the ball for 0.01 s, what was the force exerted by the player’s foot on the ball?