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course Phy 241
08/06 5:59 pm
Question: `q001. Note that this assignment contains 6 questions.
Suppose that a net force of 10 Newtons acts on a 2 kg mass for 3 seconds. By how much will the velocity of the mass change during these three seconds?
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Your solution:
10 Newtons = 10 kg*m/s^2
v = 10 kg*m/s^2 / 2kg /3 sec
v = 5 m/s^2 * 3 sec
v = 15 m/sec
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Question: `q002. By how much did the quantity m * v change during these three seconds?
What is the product Fnet * `dt of the net force and the time interval during which it acted?
How do these two quantities compare?
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Your solution:
m * v = 2 kg * 15 m/sec
m * v = 30 kg*m/sec
Fnet * dt = 10 Newtons * 3 sec
Fnet * dt = 30 kg* m/s
The quantities of both the m* v and Fnet * dt equations are exactly identical.
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Question: `q003. The quantity m * v is called the momentum of the object.
The quantity Fnet * `dt is called the impulse of the net force.
The Impulse-Momentum Theorem states that the change in the momentum of an object during a time interval `dt must be equal to the impulse of the average net force during that time interval. Note that it is possible for an impulse to be delivered to a changing mass, so that the change in momentum is not always simply m * `dv; however in non-calculus-based physics courses the effective changing mass will not be considered.
If an average net force of 2000 N is applied to a 1200 kg vehicle for 1.5 seconds, what will be the impulse of the force?
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Your solution:
Fnet = 2000N, m = 1200 kg, dt = 1.5 seconds
2000 kg * m/sec^2 * 1.5 sec
Delta p = 3000 kg*m/sec
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Question: `q004. If an average net force of 2000 N is applied to a 1200 kg vehicle for 1.5 seconds, what will be change in the velocity of the vehicle?
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Your solution:
Fnet = 2000N, m= 1200 kg. dt = 1.5 seconds
v = 2000 kg * m/s^2 / 1200 kg
v = 1.667 m/s^2 * 1.5 sec
v = 2.500 m/s
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Question: `q005. Use the Impulse-Momentum Theorem to determine the average force required to change the velocity of a 1600 kg vehicle from 20 m/s to 25 m/s in 2 seconds.
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Your solution:
m = 1600 kg, delta v = 25 m/s - 20 m/s = 5 m/s
Fnet = (1600 kg * 5 m/s) / 2 sec
Fnet = 8000 kg*m/s / 2sec
Fnet = 4000 kg*m/s^2 = 4000 Newtons
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If you understand the assignment and were able to solve the previously given problems from your worksheets, you should be able to complete most of the following problems quickly and easily. If you experience difficulty with some of these problems, you will be given notes and we will work to resolve difficulties.
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Question: `q006. ‘Each time they thought they had ‘im, his engine would explode. He’d go by like they was standin’ still on Thunder Road.’ Good song. If you don’t know it you might want to look it up and listen to it (the name is 'Thunder Road').
His car, including him and his load, had a mass of 2500 kg. To escape, he had to speed up from 35 m/s to 45 m/s. How much impulse did he need from his engine?
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Your solution:
m = 2500 kg, delta v = 45 m/s -35 m/s = 10 m/s
p = 2500 kg * 10 m/s
p = 25,000 kg*m/s
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&#Good work. Let me know if you have questions. &#