1. A brick and a pebble fall from the roof of an apartmentbuilding under constru
ID: 1733580 • Letter: 1
Question
1. A brick and a pebble fall from the roof of an apartmentbuilding under construction. At some point the brick is moving at aspeed of 3m/s and the pebble's speed is 5m/s. If both objects havethe same kinetic energy, what is the ratio of the brick's mass tothe rock's mass?a.) 25 to 9
b.) 5 to 3
c.) 12.5 to 4.5
d.) 3 to 5
2. An 800N box is pushed up an inclined plane. The plane is 4mlong and rises 2m. It requires 3200J of work to get the box to thetop of the plane. What was the magnitude of the average frictionforce on the box? a.) 0N b.) non-zero, but less than 400N c.) 400N d.) greater than 400N Any help is appreciated.
1. A brick and a pebble fall from the roof of an apartmentbuilding under construction. At some point the brick is moving at aspeed of 3m/s and the pebble's speed is 5m/s. If both objects havethe same kinetic energy, what is the ratio of the brick's mass tothe rock's mass?
a.) 25 to 9
b.) 5 to 3
c.) 12.5 to 4.5
d.) 3 to 5
2. An 800N box is pushed up an inclined plane. The plane is 4mlong and rises 2m. It requires 3200J of work to get the box to thetop of the plane. What was the magnitude of the average frictionforce on the box? a.) 0N b.) non-zero, but less than 400N c.) 400N d.) greater than 400N Any help is appreciated.
Explanation / Answer
1) let the mass of the brick is M the mass of the pebble is m given the velocity of the brick is V = 3 m/s the velocity of the pebble is v = 5 m/s if we equate theire kinetic energies we get 1/2mv2 = 1/2MV2 M / m = v2 / V2 = 25 / 9 25 to 9 2) let F is the frictional force then we have 3200 J = 2m* 800 J + F * 4m F = 400 N = 25 / 9 25 to 9 2) let F is the frictional force then we have 3200 J = 2m* 800 J + F * 4m F = 400 NRelated Questions
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