1) A 2.00×10 4 kg railroad car is rolling at 4.00 m/swhen a 1000 kg load of grav

Question

1) A 2.00×104 kg railroad car is rolling at 4.00 m/swhen a 1000 kg load of gravel is suddenly dropped in. What is the car's speed just after the gravel is loaded?

2) A 320 g bird flying along at 5.6 m/s sees a 12 ginsect heading straight toward it with a speed of 25 m/s (as measured by an observer on the ground, not by the bird). The bird opens its mouth wide and enjoys a nice lunch.What is the bird's speed immediately after swallowing?

3)A 50.0 g ball of clay traveling east at 8.00 m/scollides and sticks together with a 50.0 g ball of clay traveling north at 1.50 m/s .What is the speed of the resulting ball of clay?What is the direction of the resulting ball of clay?

4)A boat of mass 250 kg is coasting, with its engine in neutral, through the water at speed 1.00 m/swhen it starts to rain with incredible intensity. The rain is falling vertically, and it accumulates in the boat at the rate of 100 kg/hr .The drag is proportional to the square of the speed of the boat, in the form Fd=bv2 where b=0.5 N s2/m2. What is the acceleration of the boat just after the rain starts? Take the positive xaxis along the direction of motion.

5)Dan is gliding on his skateboard at 4.00 m/s . He suddenly jumps backward off the skateboard, kicking the skateboard forward at 8.00 m/s (as measured by an observer on the ground). Dan's mass is 60.0 kg and the skateboard's mass is 5.00 kg .How fast is Dan going as his feet hit the ground?

6)The skiing duo of Brian (76 kg ) and Ashley (48 kg) is always a crowd pleaser. In one routine, Brian, wearing wood skis, starts at the top of a 220-m-long, 20 slope. Ashley waits for him halfway down. As he skis past, she leaps into his arms and he carries her the rest of the way down. Hint: Use coefficient of kinetic friction from Table 6.1 in the textbook.What is their speed at the bottom of the slope?

7)A 75 kg shell is fired with an initial speed of 125m/s at an angle 55 above horizontal. Air resistance is negligible. At its highest point, the shell explodes into two fragments, one four times more massive than the other. The heavier fragment lands directly below the point of the explosion.If the explosion exerts forces only in the horizontal direction, how far from the launch point does the lighter fragment land?

Explanation / Answer

given,

initial mass = 2 * 10^4 kg

initial speed = 4 m/s

final mass = 2 * 10^4 + 1000

final mass = 21000 kg

by conservation of momentum

initial momentum = final momentum

2 * 10^4 * 4 = 21000 * v

v = 3.809 m/s

car's speed just after the gravel is loaded = 3.809 m/s

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