Session 3, week 2
Supplemental Instruction
Iowa State University / Leader: / Noah
Course: / Phys 221
Instructor: / Canfield
Date: / 09/14/14
Note that we will probably not cover everything from this sheet in each session. If you have any issues with remaining questions, bring them to the next session.
1. Draw free body (force) diagrams for each of the following situations:
(a) A bird flying through the air has a rightward force of drag equal to 4 N. The bird generates 2 N of lift and 6 N of forward force. The bird weighs 0.1 kg.
(b) A box is pushed along a horizontal surface. Friction opposes the motion with a force of 2 N. A lady pushes the box with a force of 8 N. The box weighs 8 kg and is supported by the floor.
(c) A chain hangs from the ceiling. A chandelier is supported by the chain and weighs 100 kg. A slight wind blows on the chandelier, giving it 50 m/s/s acceleration for the instant we examine the problem.
2. At the surface of Jupiter’s moon Io, the acceleration due to gravity is g=1.81 m/s2. A watermelon weighs 44.0 N at the surface of the earth.
(a) What is the watermelon’s mass on the earth’s surface?
(b) What are its mass and weight on the surface of Io?
3. To study damage to aircraft that collide with large birds, you design a test gun that will accelerate chicken-sized objects so that their displacement along the gun barrel is given by
x = (9.0 x 103 m/s2) t2 – (8.0 x 104 m/s3)t3. The object leaves the end of the barrel at t = 0.025 seconds.
(a) How long must the gun barrel be?
(b) What will be the speed of the objects as they leave the end of the barrel?
(c) What net force must be exerted on a 1.50 kg object at t = 0 seconds and t = 0.025 seconds?
4. A force of magnitude 7.50N pushes three boxes with masses m1: 1.30kg, m2: 3.20kg, and m3: 4.90kg. The force is applied to box number three. Find the magnitude of the contact force
(a) Between boxes 1 and 2
(b) Between boxes 2 and 3
5. In a head on auto-collision, passengers not wearing seatbelts can be thrown through the windshield. Use Newton’s Laws of Motion to explain why this happens.
6. Which has a greater weight: An 8kg mass on Earth, with a gravitational acceleration of 9.81 m/s/s or a 4 kg mass on a foreign planet where the gravitational acceleration is 14 m/s/s.
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