Worksheet

1. A man is hanging froma clothesline that is attached to a pole at both ends. Thne man is hanging rith in the middle of the line with a force of 600N. The clothes line makes a 8deg angle with the horizontal. Find the tension in the rope on either side of the performer.

Since the angles on both sides are the same, the tesion in both wires is going to be the same, so the only direction I need to concern myself with is the y direction. Notice how large the tension is here. As the limit of this angle goes to zero, the sin function takes the tension to infinity. That is why the strong man contest we did in class does not work. You would need an infinite tension in the wire fro the angle to be zero(string to remain horizontal).

2. Three cables support a 150N bird feeder, find the tension is all three cables.

First apply Newton's Second Law to y direction.

Now apply Newton's second Law to x direction

Now take the result from the x direction and substitute it into

the y directions and solve for on of the tensions

Now substitute back into x direction for T1

T1 = 130N

3. A 1kg mass is observed to accelerate at 10m/s^2 in a direction 30deg nort of east. One of the two forces acting on the mass has a magnitude of 5N and is directed due north. Determine the magnitude and direction of the second force acting on the mass.

This problem is a little different, but still use Newton Second Law.

The way to look at this problem is the think about the block accelerating due north and you need to apply a force (Fapp) to cause the block to move at 10m/s^2 30deg north of east.

We will start by looking at the x direction

Now you now the mass, but not the acceleration. Ahh, but you do know the acceleration. Acceleration is a vector like force or velocity, it can be broken into components, so do it. Use just the y component since that is the direction we are concerned with.

First thing that I am going to do is calculate the weight, because I can see that T3 and the weight have to have the same value.

Now I am going to apply Newton's Second Law to the y direction.

Now do the exact same thing for the x direction

Now take the value that you found for T1 in the x direction and apply it to the y direction.

5. The distance between two telephone poles is 50m. When a 1kg bird lands on the telephone wire midway between the poles, the wire sags 0.2m. How much tension does the bird produce in the wire?

First thing I am going to do is find the weight

Now I am going to calculate q

Now use Newton's second law to calculate tension in the wire. The tension is the same for both sides.

6. A 0.51kg baseball moving at 20m/s strikes the glove of a catcher. The glove recoils a distance of 8cm. What average force does the glove exert on the ball? What average force does the ball exert on the glove?

The force for ball to glove and glove to ball would be the same, depending on refernce frame

7. A train has a mass of 5.22 X 10^6kg and is moving with a speed of 90km/h. The engineer applies the brakes, which results in a net backward force of 1.87 X 10^6 N on the train. The brakes are held for 30s.

Now that you have the acceleration, just use a kinematic equation to find the final velocity of the train after 30s.

You already have enough information to solve this problem. Just use one of the equations.

8. The parachute on a 900kg racecar opens at the end of the race, when the car is traveling at 35m/s. What total retarding force force must be supplied by the parachute to stop the car in a distance of 1000m?

You need to use the information given to find acceleratation

9. A 5kg bucket of water is raised from a well by a rope attached to the bucket. If the upward acceleration of the bucket is 3.0m/s^2, find the force exerted on the bucket by the rope.

First thing I will do here is calculate the weight of the bucket

Now apply Newton's Second Law

10. A 5kg mass placed on a frictionless, horizontal table is connected to a cable that passes over a pulley and then is fastened to a hanging 10kg mass. Find the acceleration of the two objects and the tension in the string.

Now apply Newton's Second Law

Now Look at the other block and find T so you can substitute it here and solve for the acceleration.

Now substitute this tension back into the the result for the previous block and solve for the acceleration

The tension is going to be the same, so just substitue back and find the tension

T = 98N