Momentum Problems!!!!!!!!!!!!!!!!!!!!!!?
I need help on these problems. I know the answers but not sure how to solve…
1) A 50g golf ball is struck with a club. (The ball is sitting on the tee.) The force on the ball varies from zero when contact is made up to some max. value (when the ball is deformed) and then back to zero when the ball leaves the club. Assume that the ball leavves the club face with a velocity of zero.
a) Estimate the size and direction of the impulse due to the collision.
b. Estimate the duration of the collision and the average force on the ball. Assume that the ball travels the distance of its radius during the time its contact with the club, the radius is 2.0 cm.
2. How good are the bumpers?
In particular crash test, a car of mass 1.50 times 10 to the third kg. collides with a wall. The initial and final velocities of the car are vi=-15.0 m/s and vf=+2.60 m/s respectively. If the collision lasts for 0.160 find the impulse on the car due to the collision and the size and direction of the average force exerted on the car.
3. The Recoiling Pitching Machine:
Chad, a baseball player, wishes to keep his physical; condition during the winter. He uses a 50 kg pitching machine to help him, placing the machine on the pitchers mound. The ground is covered with a thin layer of ice, so that there is negligible friction between the ground and machine. The machine fires a 0.15 kg baseball horizontally with a speed of 36 m/s. What is the recoil speed of the machine?
4. Cars and Trucks colliding:
Most of us know intuitively that in a head on collision between a large dump truck and a compact car, you are better being in the truck than in the car. Why is this? Many people imagine that the collision force exerted on the car is greater than the truck, and they point out that the car experiences more damage than the truck. This reasoning of unequal forces is false, of corurs.e Newton’s 3rd law tells us that both objects experience equal forces. The truck suffers less damage because it is made of stronger metal but what about the 2 drivers? Do they experience unequal forces? To answer this ?. suppose that each vehicle is moving 8m/s and they undergo a collision where the cars become stuck together. Each driver has a mass of 80kg. Including the drivers, the total vehicle masses are 800 kg for the car and 4,000 for the truck. If the collision time is 0.120, what force does the seat belt exert on the driver??
Thanks for your help:)
One Response
Dodeca Dave
09 Feb 2010
1) a)
You want to understand that an impulse is an amount of momentum.
↑↑↑↑↑↑↑↑↑↑↑
Important !
Which is.. P= mv. However in this question you are not given a velocity, maybe you just guess one. I will call it V. The impulse is mV in the forward direction.
b) You want to understand that force is the RATE OF CHANGE OF MOMENTUM. F=dP/dt,
↑↑↑↑↑↑↑↑↑↑↑
Important !
Therefore P= Impulse = I = ∫Fdt
If you pretend the force is constant then don’t need to integrate and you have P=I=FΔt
V is the velocity of the club
To find the time the ball is in contact use v=d*t
P=I=mV=FΔt , you can solve for F
2) This is easier then the first one.Again remember an impulse is an amount of momentum, or, P=I= mv. Find the difference in velocity, and plug it into I=mv
Assume the force is constant and use P=I=FΔt
3) use the conservation of momentum law.
4)
a) Because of the conservation of momentum law the change of velocity of the truck will be less. (greater mass)
b) This part is hard.
Use the conservation of momentum to find the final velocity of the car and truck stuck together.
v₁m₁ +v₂m₂ = v(m₁+m₂)
Then calculate the change in velocity of the driver.
You know his mass and therefore his change in momentum
Assuming the force is constant you can use the simple version of the impulse equation. P=I=FΔt, solve for F
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