physics math

PHYSICS 254 EXAM 3 Fall 2021

Dr. Jennifer Cash

Name _____________________________

SHOW ALL WORK, USING THE BACK OF A PAGE IF NECESSARY. DRAW A BOX AROUND THE FINAL ANSWER.

For questions 1-6, either indicate the correct answer in the blank or select the answer which most correctly answers the question. These questions do not require calculations and you do not have to show your work. Please clearly indicate your answers!!

1) For each of the following variables, list the symbol used in equations to represent it and the units you would expect for it: (1 pts each)

symbol unit

(a) angular velocity ______ ______

(b) angular acceleration ______ ______

(c) period ______ ______

(d) momentum ______ ______

(e) force ______ ______

2) In the equation, Σ τ= I α , the symbol τ is called? (1pt)

a) Tension b) Tangential c) Torque d) Time

3) In the equation, Σ τ= I α , the symbol I is called? (1pt)

a) Inertia b) Impulse c) Initial d) Instantaneous

4) In an elastic collision, which of the following MUST be true? (2 pt) a) momentum is conserved, but kinetic energy is not

b) kinetic energy is conserved, but momentum is not c) neither momentum nor kinetic energy are conserved d) both momentum and kinetic energy are conserved

5) For the diagram shown to the right a particle is moving clockwise around the circle. Draw an arrow in the direction of the centripetal acceleration at point H and E (2 pts)

6) A child is playing with a birthday present “barrel of monkeys” by hanging his monkeys along a ruler. He places one small monkey with a mass of m1 at a distance of r1 from the center pivot point and one bigger monkey with a mass of m2 at distance of r2 from the pivot point as shown in the diagram below. The pivot point is located at the geometric center of the ruler.(6pt)

Construct the FULL torque equation for this situation (Note you are not solving the equation or plugging in values)

For problems 7-12 , you need to SHOW YOUR WORK, and may get partial credit if your work demonstrates your understanding of the concepts.

Clearly indicate your final answer!!!

7) Ira spins the propeller on his drone helicopter around through an angle of 24,500 degrees, what is this angle in revolutions? (3 pts)

8) Ira spins his fidget spinner around through an angle of 75.2 revolutions, what is this angle in radians? (3 pts)

9) An average of force of 1250 N is applied to a block over a short time interval resulting in an impulse of 53.8 Ns. What was the time span during which the force acted? (6 pts)

10) A large 25.0 kg solid sphere with a radius of 1.24 m is rolled along the floor. Calculate the moment of inertia for the sphere. (clearly show the equation you are using) (6 pts)

11) A force of 12.0 N is applied to the end of a 3.12 m beam at a 35o angle as shown in the figure to the right. Calculate the torque applied to this beam? (6 pts)

12) Calculate the momentum of a garbage truck that is 13500 kg and moving to the right at 12.5 m/s? (6 pts)

Questions 13-19, all related to the following word problem, You must answer ALL questions on this page (6 pts each)

Ira flies a 0.750 kg toy airplane connected to string at a constant tangential speed of 5.36 m/s such that the plane goes once around a circular path every 0.75 seconds.

13) Calculate the radius of the circular path

14) Calculate the centripetal acceleration on the toy airplane.

15) Calculate the force of the string keeping it in circular motion

16) Calculate the angular velocity of the toy airplane

(The following problem will be worth 24 points)

(SHOW ALL WORK!!! including your knowns, what you are solving for, equations, units, diagrams, and the solution; partial credit is given for the problem setup as well as the solution)

A flywheel accelerates from an angular speed of 5.80 rad/s to an angular speed of 22.2 rad/s with a constant angular acceleration of 6.12 rad/s2. Calculate a) the time for this motion and b) the angular displacement of the flywheel during this motion.

Knowns: (symbols, numbers, and units) Solving for: (symbols/words)

a)

b)

Equations: (in symbols)

Math:

Final Answers: (including units)

a) b)