Net Impulse Question: Calculate Momentum, Impulse, and Change in Momentum

In summary, the conversation discusses the net force acting on a glider on an air track and its corresponding diagram. The glider has a mass of 0.850 kg and an initial velocity of 0.100 m/s in the positive direction of the x-axis. The momentum of the glider at t = 0.00 s is calculated by multiplying the mass by the initial velocity. The net impulse imparted to the glider between t = 0.00 and t = 0.60 s is calculated using the average force and time, resulting in a value of 4.5N-s. The change in momentum of the glider over this time interval is equal to the net impulse. Finally, the instantaneous velocity
  • #1
hhq5000
6
0

Homework Statement




The net force acting on a glider on an air track (an essentially frictionless system) varies with time as shown in the following diagram. The vertical scale is such that the space between consecutive vertical gridlines is 5.0 Newton(s).


The glider has a mass of 0.850 kg. When the force is applied to the glider at clock reading t = 0.00, the glider has an initial instantaneous velocity of 0.100 m/s in the positive direction of the x-axis.
(a) Calculate the momentum of the glider at t = 0.00 s (i.e., the initial momentum).
kg·m/s
(b) Calculate the net impulse imparted to the glider by the applied net force between t = 0.00 and t = 0.60 s.

N·s
(c) Calculate the change in momentum of the glider over this time interval.


(e) Calculate the instantaneous velocity of the glider at clock reading t = 0.60 s.
m/s




Homework Equations


change in momentum= pf-pi

I=(Fav)(DeltaT)

The Attempt at a Solution



i tried to use the the Impulse equation and did (15N)(.6seconds). I also attempted to use the change in momentum equation and was missing the velocity of the final. I need help with b-e.
 

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  • #2
first, the impulse is as you describe, but since the area is a triangle the total impulse is 1/2(15*.6)= 4.5N-s

I assume you had no problem computing the initial P. The change then is equal to the impulse, just as you have stated. Throw some numbers out and we'll see how that look.
 
  • #3


a) The initial momentum of the glider can be calculated using the formula p=mv, where m is the mass of the glider and v is the initial velocity. Therefore, the initial momentum is (0.850 kg)(0.100 m/s) = 0.085 kg·m/s.

b) To calculate the net impulse, we can use the formula I=FΔt, where F is the average force and Δt is the time interval. The average force can be calculated by finding the area under the curve in the given diagram. Since the force varies with time, we can divide the time interval into smaller intervals and calculate the average force for each interval. Then, we can add all the average forces together to get the total average force. In this case, we can divide the time interval into two intervals: t = 0.00 to t = 0.30 s and t = 0.30 to t = 0.60 s. The average force for the first interval is (15N + 5N)/2 = 10N and for the second interval is (5N + 10N)/2 = 7.5N. Therefore, the total average force is 10N + 7.5N = 17.5N. Now, we can plug in the values into the impulse equation: I=(17.5N)(0.60s) = 10.5 N·s.

c) To calculate the change in momentum, we can use the formula Δp = pf - pi, where pf is the final momentum and pi is the initial momentum. The final momentum can be calculated by using the formula p=mv, where m is the mass of the glider and v is the final velocity. We can calculate the final velocity by using the formula v= u + at, where u is the initial velocity, a is the acceleration (which can be calculated by using the formula F=ma), and t is the time interval. Since the glider is moving in the positive direction, the acceleration is also in the positive direction. Therefore, we can use the formula F=ma to find the acceleration: a = F/m = (17.5N)/(0.850 kg) = 20.59 m/s^2. Now, we can plug in the values into the final velocity formula: v = (0.100 m/s) + (20.
 

1. What is the difference between momentum and impulse?

Momentum is a measure of an object's motion, calculated by multiplying its mass and velocity. Impulse, on the other hand, is a change in momentum, calculated by multiplying the force applied to an object and the time it acts on the object.

2. How do you calculate momentum?

The formula for momentum is momentum = mass x velocity. This means that you multiply the mass of an object by its velocity to get its momentum.

3. What units are used to measure momentum and impulse?

Momentum is typically measured in units of kg*m/s, while impulse is measured in units of N*s or kg*m/s.

4. How do you calculate change in momentum?

Change in momentum is calculated by subtracting the final momentum from the initial momentum. This can also be represented by the formula change in momentum = final momentum - initial momentum.

5. How can calculating net impulse be useful in physics?

Calculating net impulse can be useful in understanding the changes in an object's motion due to external forces. It can also be used to predict the outcomes of collisions and other interactions between objects.

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