Two blocks are being pushed across a horizontal floor with a coefficient of kine
ID: 1419806 • Letter: T
Question
Two blocks are being pushed across a horizontal floor with a coefficient of kinetic friction mJ.3.The mass of block Ais 3kg, and the mass of block B is 2 kg. 1) If the force being applied by the finger is F, what is the force that block A applies to block B? AonB F AonB F/2 2F/5 AonB 2) If the force applied by the finger is F 20N, what is the acceleration of the blocks? a 68 m/s O a -.94 m/s a 31.06 m/s 3) If the force applied by the finger was doubled, the acceleration of the blocks would be: less than twice as much O exactly twice as much more than twice as muchExplanation / Answer
In this problem, we need to determine the ratio of the force that that block A applies to block B compared to the total force. The easiest way to solve this problem is to determine a force that is large enough to cause the block’s accelerate.
If you look at the drawing, you can see that the applied force is causing both blocks to accelerate. To determine the fraction of the force that represents the force that block A exerts on block B, we need to determine the fraction of the total mass that is block B’s mass. This is 2/5. So, the last answer is correct. (Answer to 1st)
To prove that this is true, let’s determine the total friction force.
Ff = 0.3 * 5 * 9.8 = 14.7 N
For the block’s to accelerate, the applied force must be greater than the friction force. Let’s assume that the applied force is 20 N
Net force = 20 – 14.7 = 5.3 N
To determine the acceleration, divide by 5
a = 5.3/5 = 1.06 m/s (Answer to 2nd)
Since this is the acceleration of block B, let’s use the following equation to determine the force that block B is exerting on block A.
Net force on A = F – Ff = m * a
Ff = 0.3 * 2 * 9.8 = 5.88
F – 5.88 = 2 * 1.06
F = 5.88 + 2.12 = 8 N
Let’s determine what fraction this force is of the applied force
Fraction = 8/20 = 0.4
This is 2/5.
This proves that my answer is correct.
If force is doubled, acceleration would be more than twice as much. (Answer to 3rd)