4) Alex, Ben, and Chris are trying to move a heavy rock of mass 250 kg. Alex pul
ID: 1348484 • Letter: 4
Question
4) Alex, Ben, and Chris are trying to move a heavy rock of mass 250 kg. Alex pulls the rock North with a force of 500 N, Ben pushes the rock East with a force of 450 N and Chris pulls the rock with a force of 540 N at an angle 37.0 degrees East of North. Despite their commendable attempts, the rock refuses to move. Calculate the magnitude of static friction force on the rock.
Answer:
5) Three blocks, A, B and C, are lined up in that order on a smooth horizontal surface and have masses 11 kg, 27 kg and 34 kg respectively. Blocks A and C are in contact with block B. You push block A towards block C with a constant horizontal force of 20 N. In the first answer box enter the magnitude of normal force that A exerts on B. In the second answer box enter the magnitude of normal force that B exerts on C.
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Answer 2 of 2:
6) After a hard day's work, you return home and decide to clean your apartment. In order to do so, you need to move your bed which has a mass of 100 kg. You exert a horizontal force of 300 N and your bed refuses to move. You roll up your sleeves and keep pushing until you exert a horizontal force 600 N. The bed slides a little but now you are exhausted and stop pushing. You have an aha! moment as you recall what you learned in Physics 101. Consequently, you remove the bed's mattress (37 kg) and push the bed again with the same horizontal force as before. This time the bed slides with an acceleration of 4.12 m/s^2. In the first answer box, enter the co-efficient of static friction between the bed and the floor. In the second answer box, enter the co-efficient of kinetic friction between the bed and the floor.
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7) A ladder rests against a smooth vertical wall. The magnitudes of the normal forces from the wall and floor on the ladder are 38 N and 68 N respectively. In the first answer box enter the mass of the ladder and in the second answer box enter the magnitude of static friction force from the floor on the ladder.
Answer 1 of 2:
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Explanation / Answer
given,
mass of the rock = 250 kg
Alex pulls the rock North with a force of 500 N
Ben pushes the rock East with a force of 450 N
Chris pulls the rock with a force of 540 N at an angle 37.0 degrees East of North
since the rock remains at rest so net force = 0
total horizontal force = 0
450 + 540 * sin(37) - static friction force = 0
static friction force = 774.98 N
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