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# A boy drags a wooden crate with a mass of 20 kg, a distance of 12 m, across a rough level floor at a constant speed of 1.5 m/s by pulling on the...

1. A boy drags a wooden crate with a mass of 20 kg, a distance of 12 m, across a rough level floor at a constant speed of 1.5 m/s by pulling on the rope tied to the crate with a force of 50 N. The rope makes an angle of 25° with the horizontal.

a. What are the horizontal and vertical components of the applied force?

b. What is the magnitude of each of the forces?

c. How much work is done by each of the forces?

d. What is the total amount of work done on the object?

e. What is the coefficient of friction of the crate on the floor?

2.Two 2 charges of 9 mC and 4mC are placed a distance of 4m apart.

a. Calculate the magnitude and direction of the force on a positive 5 mC charge at the midpoint between the two charges.

b. Find the point between the two charges where the force on the 5 mC charge is 0?

3. A 0.05 kg arrow is launched vertically in the air. The bowstring exerts an average force of 53 N on the arrow over a distance of 0.75 m.

a. With what speed does the arrow leave the bow.

b. How high will the arrow travel? Neglect air resistance.

4. A boy with a mass 50 kg walks up the stairs from the ground to the top of a spiral water slide in 1 minute. The height of the slide is 11.5 m above the ground.

a. calculate the following:

(i) the potential energy gained

(ii) the average power developed by the boy in walking up the stairs

b. As the boy slides down the slide and reaches the bottom, his speed is 12 m s-1 and the distance traveled along the slide is 108 m.

(i) Find the mechanical energy lost by the boy in sliding down the slide.

(ii) What is the average frictional force acting on the boy?

5.A 3.0 µF capacitor charged to 40 V and a 5.0 µF capacitor charged to 18 V are connected to each other, with the positive plate of each connected to the negative plate of the other.

a. Find the final charge on each capacitor.

b. Find the potential difference across the capacitors.

6.parallel plate capacitor has an area A=10 m^2 and a separation of 1*10^-4m.

a. What is the capacitance of this capacitor?
b. How much energy is stored in this capacitor when it is charged to a potential of 100V?
c. How much charge is stored on the capacitor?
d. If a material with a dielectric constant e=200 is inserted between the plates of the capacitor and it completely fills the area, what is the capacitance?

7. A charge of +18 mC is on the y axis at y=+3.0 m. A charge of -12 mC is at the origin. A charge of +45 mC is on the x axis at x=+3.0 m.

a. Determine the magnitude of the net electrostatic force on the charge at x=+3.0 m.

b. Find the direction of the force relative to the -x axis.

8. A charge of +10 mC is at (+3 m, 0m) on the x-axis and a charge of +10 mC is at (-3 m,0 m).

a. Determine the work required to assemble this charge distribution.

b. Find the magnitude of the electric field at a point (0,+3m) on the y-axis.

c. A charge q = +1.0 mC is placed at this point. Find the magnitude of the force on the charge

9.A charge of 4nC is moved from infinity to a point 15cm away from a charge of 8nC.

a. What is the potential energy needed to do this?

b. What is the potential at the point where the 7 nC charge is placed?

c. How much potential energy is needed to move a 7nC charge from infinity to that point?

10.Water waves in a tank are 10 cm long. The waves pass a point at the rate of 3.75 waves/sec,

a. What is their speed?

b. What is their period?

11.A string has a total length of 5 m and a total mass of 0.01 kg. If the string has a tension of 10N applied to it, what is the speed of a wave on this string?

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