How Do You Solve These Physics Homework Problems?

[surma884]

Ooops, sorry I posted in the wrong forum.

Here are the problems. I have no idea where to start! I don't want the answer I just want a little clue to get me started.

Scenario: Two packages at UPS start sliding down a 20 degree ramp, and package A is in front of package B. Package A has a mass of 4.50 kg and a coefficient of kinetic friction of 0.200. Package B has a mass of 10.5 kg and a coefficient of kinetic friction of 0.140.
Question: How long does it take package A to reach the bottom?

Scenario: Two blocks are hanging off a pulley by a string. One block on the left and the other on the right. A 100 kg block takes 5.90s to reach the floor after being released from rest.
Question: What is the mass of the other block?

Question: A house painter uses a chair and pulley arrangement to lift himself up the side of a house. The painter's mass is 70 kg and the chair's mass is 10 kg. With what force must he pull down on the rope in order to accelerate upward at 0.20m/s^2

If someone could just explain to me the steps I should take to go about solving these problems. BTW, I am clueless about the formulas. I only know Force = mass*accelaration.

 

[NateTG]

The typical approach for dealing with problems like these is to start by drawing a free body diagram.
Once you have a free body diagram, you can figure out expressions for the net force on the object that you're interested in.
Using the expression for net force, you can apply F=ma.

 

[wais]

First of all, don't worry about posting in the wrong forum. We all make mistakes sometimes. It's great that you're seeking help and just need a little guidance. I'll try my best to explain the steps for solving these problems.

For the first problem, we need to use the formula F_friction = μ*mg to calculate the frictional force acting on package A. Here, μ is the coefficient of kinetic friction, m is the mass of the object, and g is the acceleration due to gravity (9.8 m/s^2). Once we have the frictional force, we can use Newton's second law (F = ma) to find the acceleration of package A. From there, we can use the kinematic equation v = u + at (where v is final velocity, u is initial velocity, a is acceleration, and t is time) to calculate the time it takes for package A to reach the bottom of the ramp.

For the second problem, we can use the fact that the two blocks are connected by a string and therefore have the same acceleration. We can use Newton's second law again to find the acceleration of the blocks, and then use the kinematic equation s = ut + 0.5at^2 (where s is the distance, u is initial velocity, a is acceleration, and t is time) to find the distance the blocks fall. Since we know the time it takes for the first block to reach the floor, we can use this distance to calculate the acceleration of the blocks. Then, we can use the same formula to find the mass of the other block.

For the third problem, we can use Newton's second law again to find the net force acting on the painter-chair system. Since the painter is accelerating upwards, the net force must be greater than the weight of the system (mg). We can use the formula F = ma to find the net force, and then subtract the weight of the system to find the force the painter must pull down on the rope with.

I hope this helps give you a starting point for solving these problems. Remember to always start with the given information and use the appropriate formulas to find the unknown quantities. Good luck!