Phys 221 SI Worksheet:
Forces
Supplemental Instruction
Iowa State University
Leader:
Course:
Instructor:
Date:
Justin
Phys 221
Rosenberg
2/4/14
1. A block with mass m=5.0kg sits on an inclined plane. The angle of the plane with the
horizontal is 25 degrees. A force F is applied to the block at an angle 20 degrees above
the incline up the ramp. What is the minimum value of F to keep the block from sliding
down the ramp?
2. A particle revolves in a horizontal circle of radius 2.0 m. at a particular instant, its
acceleration is 2.0m/s/s in a direction that makes a 110 degree angle to its direction of
motion. Determine its speed at this moment, and at a moment 2.50s later assuming a
constant magnitude of tangential acceleration.
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3. Block A has a mass of 4kg. Block B has a mass of 3kg. Block C has a mass of 1kg. The
blocks are arranged side by side on a frictionless surface in the following order: A, C, B.
a 15N force is applied to block A, pushing the blocks across the surface. What is the net
force acting on each block? What is the magnitude of the contact forces between each
block? If block C is now replace with a loaf of bread (or some other object easily
squished), which arrangement of the three objects would result in the flattest loaf of
bread?
4. Three blocks of mass m1=1.0kg, m2=2.0kg, and unknown mass m3 are on a frictionless,
horizontal surface as shown on the board. The blocks are connected by ideal, massless
strings. A force Fr=33N is applied to the right block, and is directed to the right. The
tension T12 in the string between m1 and m2 is not known and the tension T23 in the
string between m2 and m3 is 24N. What is the tension T12? What is the mass, m3?
5. You are riding on a ferris wheel with a radius of 80m that is rotating with a constant
angular velocity of 2rpm. If you are sitting on a scale, what will the scale report your
weight, in newtons, as at the top, at the right most points of your trajectory, and at the
bottom of the ride if your mass is 82kg.