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Help on numbers 3-8? Please. Safari File Edit View History Bookmarks Window Help 100% . Sat 6:16 PM Q. encapa 3) A speoding car is going 72 mi/fhr. The driver hits the brakes to slow the car down to the 55 mi/hir speed limit. The car has a mass of 2.0 mctric tons. What is the magnitude of the impulse exerted by the brakes on the car? Answer: Submit All Answers 4) Humpty Dumpty sat on a wall. Humpty Dumpty had a big fall. If Humpty Dampty's mass is 14 kg, and the wall's height is 4 meters, how much impulse did gravity exert on Humpty Dumpty during his fall? (Humpty Dumpty is pretty acrodynamie, so you can neglect air resistance) Answer: Submit Al Answers fic to start moving when a truck rear-ends you, boosting your car's speed to 4 mihr 5) During a spate of stop-and-go traffic on the highway, you are twiddling your thumbs, Waiting for the tra The truck's speed is 0.00 mi/hr after the collision. What was the truck's speed before it col that you can neglect effects like friction in your analysis. before it collided with you? Assume that the trock is about 4 times more massive than your car. Also, assume Answer: Submit All Ardwers 6) Suppose that you are driving along at a slow, steady rate of 12.00 mi/hr when the same truck from before rear -ends you, boosting your car's speed to 15.00 mi/har. The truck's speed is 12.25 was the truck's initial speed before the collision? Assume that you can neglect effects like friction in your analysis Answer: mass 1.8 metric tons, collide head-on during a crash-test. One car was moving at speed 52 mihr before the collision, the other car was moving at 62 mi/hr. After the collision, the two cars skid together until they come to rest. What was the total impalse magnitude exerted by friction on the cars after the collision? Answer: Submit All Answers 8) Consider the same situation as before, only after the crash, the cars skid for a short distance before ending up on an oil slick and sliding approximately frictionlessly with a final speed of I mihr. What was the impulse magnitude exerted on the two cars by friction while they were skidding, up until they reached the oil slick? 4

Explanation / Answer

3. vi = 72 x 1609 m / 3600 s

vi = 32.18 m/s

vf = 55 x 1609 m / 3600s = 24.6 m/s

m = 2000 kg

impulse = change in momentum = m (vf - vi)

= 15196 kg m/s .....Ans

4) v = sqrt(2 g h ) = 8.85 m/s

impulse = 14 x 8.85 = 124 kg m/s

5) pi = pf

(4 m v) + (m x 0) = (4m x 0) +(m x 4mi/hr)

v = 4/4 mi/hr = 1 mi / hr

6) (4m x v) + (m x 12) = (m x 15) + (4m x 12.25)

4 v + 12 = 15 + 49

v = 13 mi/hr

7) v1 = 52 mi/hr = 23.24 m/s

v2 = 62 mi/hr =27.7 m/s

vf = (27.7 - 23.24)/2 = 2.14 m/s

impulse = (1800 kg) (27.7 - 2.14)

= 46000 kg m/s

8) vf = 0.45 m/s

impulse = (2 x 1800) (2.14- 0.45)

= 6084 kg m/s

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