Three students push horizontally on a large 80 kg crate sitting on the floor. Two of them push to the left on the crate, each with a force of 170N. The third pushes to the right on the crate with a...

Three students push horizontally on a large 80 kg crate sitting on the floor. Two of them push to the left on the crate, each with a force of 170N. The third pushes to the right on the crate with a force of 150N. Assume that no friction acts on the crate. What is the acceleration of the crate and what will happen to the net force and acceleration if a fourth student jumps on top of the crate.

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justaguide | College Teacher | (Level 2) Distinguished Educator

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Three students push horizontally on a large 80 kg crate sitting on the floor. Two of them push to the left on the crate, each with a force of 170 N. The total force applied towards the left by the students is 170*2 = 340 N. The third student pushes to the right on the crate with a force of 150 N. Force is a vector and the direction in which it acts is relevant. The net force acting on the crate is 340 - 150 = 190 N towards the left. As the mass of the crate is 80 kg, the acceleration of the cage due to the forces exerted by the students is 190/80 = 2.375 m/s^2 towards the left.

If a fourth student jumps on top of the crate there is no change in the net force acting on the crate. But as the mass of the student is a positive number there is an increase in the total mass; this results in a decrease in the acceleration of the crate.

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