# Circular motion, unbalanced-balanced forces

Question 1
A box of mass 5.8 kg is pulled to the right with a horizontal force of 8.2 N. If the box moves to the right with constant velocity of 2.66 m/s, what is the frictional force acting on the box?

Question 3
A person pulls on a 41 kg table with a 215 N force acting at an angle of 39 degrees above the horizon. The desk does not budge. What is the coefficient of friction, between the table and the floor?

Question 5
The driver of a 1085 kg truck travelling 27.0 m/s, North on I-77, has to make a sudden stop. If it requires a distance of 57.7 m for the truck to stop, what is the net force on the truck?

Question 7
A 14 kg box is placed at the top of a 5.1 m long, frictionless ramp inclined at an angle of 35 degrees. How long does it take the box to reach the bottom of the ramp?

Question 9
A 786 kg car travels from Boone to Blowing Rock along US 321. What net force is required to keep the car traveling at a constant speed of 29.1 mph (13 m/s) around a curve of radius 33.5 m?

Question 11
A 14 kg box is placed at the top of a 4.9 m long, ramp inclined at an angle of 35 degrees (with the horizon). However, the ramp is covered with sand so the coefficient of friction is now 0.17. How much time does it take the box to reach the bottom of the ramp?

Question 13
The following forces act on a hockey puck sitting on a frictionless surface: F1 = 10.3 N at 15 degrees; F2 = 26.3 N at 125 degrees; and F3 = 36.4 N at 235 degrees. (All the forces are in the plane of the ice.) What is the net force on the puck?

Question 15
A Modified Atwood’s Machine (the pulley, 2 mass system used in class and in the Modified Atwood physlet) has a 10. N cart on a frictionless, horizontal track with a 10. N hanging weight attached to string connecting the two weights. A second track is set up with the hanging weight replaced by a person who can maintain a 10. N pull on the string (as measured with a force probe). Which set-up has the greater acceleration?

## Answers and Replies

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haruspex
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Please study the rules for posts on this forum. Like, one thread per question, a statement of the equations you believe you are expected to use, and some attempt at solution. If any diagrams are relevant, post those or a good verbal description.

Simon Bridge
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Welcome to PF;
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