PHY 113: General Physics 1
Practice Problems and Solutions (by former students!)
Measurements
 Use dimensional analysis to determine the units of G:
F=G(m_{1}m_{2})/r^{2}
if F is has units of kg m/s^{2}, m_{1} and m_{2} have units of kg, and r has units of m.
Kristen Shumaker (Spring 2014)
Motion in One Dimension
 The position of a particle moving along the x axis is given by x = (21 + 22t  6.0t^{2})m, where t is in s. What is the average velocity during the time interval t = 1.0 s to t = 3.0 s?
Bree Wilhite (Spring 2014)
 The driver of a car slams on the brakes when he sees that he is about to run into a tree. The car slows down uniformly with an acceleration of 5.60 m/s2 for 4.2 s, making skid marks 62.4 m long that ends at the tree. What is the velocity of the car exactly when it hits the tree? (Hint: the answer is not zero)
Killian Wustrow (Spring 2014)
Motion in Two Dimensions
 A track star in the broad jump goes into the jump at 12 m/s and launches himself at 20° above the horizontal. How long is he in the air before returning to Earth?
Bryson Rominger (Spring 2014)
 A ball is thrown horizontally from the top of a building 0.10 km high. The ball strikes the ground at a point 65 m horizontally away from and below the point of release. What is the speed of the ball just before it strikes the ground?
Amanda McAneny (Spring 2014)
 A crate of mass m is placed on an incline with θ=30°. a) What is the acceleration of the crate as it slides down the incline?
b) Starting from rest, the crate travels a distance d=10.2 m to the bottom of the incline. How long does it take to reach the bottom?
Eric Kandigan (Spring 2014)
Laws of Motion
 In the figure shown, the coefficient of kinetic friction between the block and the incline is 0.40. What is the magnitude of the acceleration of the suspended block as it falls? Disregard any pulley mass or friction in the pulley.
Caroline Lynott (Spring 2014)
 If F = 40 N and M = 1.5 kg, what is the tension in the string connecting M and 2M? Assume that all surfaces are frictionless.
Ryan Dunlow (Spring 2014)
 If M = 2.0 kg, what is the tension in string 1?
Lindey Campagne (Spring 2014)
 If a = 40° and the tension in string 2 is 30 N, determine M, the mass of the two objects.
Fabrice Momo (Spring 2014)
Circular Motion
 A race car moving with a constant speed of 60 m/s completes one lap around a circular track in 50 s. What is the magnitude of the acceleration of the race car?
Bailey Goodwin (Spring 2014)
 A satellite is in a circular orbit 600 km above the Earth's surface. The acceleration of gravity is 8.21 m/s^{2} at this altitude. The radius of the Earth is 6,400 km. Determine a) the speed of the satellite, and b) the time to complete one orbit around the Earth. (Hint: For (a), note the direction of the acceleration of gravity.)
Grace Yook (Spring 2014)
Energy of a System
 A block is pushed across a rough horizontal surface from point A to point B by a force (magnitude P = 5.4 N) as shown in the figure. The magnitude of the force of friction acting on the block between A and B is 1.2 N and points A and B are 0.5 m apart. If the kinetic energies of the block at A and B are 4.0 J and 5.6 J, respectively, how much work is done on the block by the force P between A and B?
Carson Wigley (Spring 2014)
 A quarterback throws a football of mass 0.15 kg at a speed of 40 m/s and initial angle of 30°. What is the kinetic energy of the football at the highest point of the trajectory? (Hint: The answer is not 0 J.)
Chirag Patel (Spring 2014)
 The horizontal surface on which the block slides is frictionless. The speed of the block before it touches the spring is 6.0 m/s. How fast is the block moving at the instant the spring has been compressed 15 cm? k = 2.0 kN/m
Crystal AgueroNorman (Spring 2014)
Conservation of Energy
 A 0.04 kg ball is thrown from the top of a 30 m tall building (point A) at an unknown angle above the horizontal. As shown in the figure, the ball attains a maximum height of 10 m above the top of the building before striking the ground at point B. If air resistance is negligible, what is the value of the kinetic energy of the ball at B minus the kinetic energy of the ball at A (K_{B} − K_{A})?
Erin Christensen (Spring 2014)
 A 0.80 kg object tied to the end of a 2.0 m string swings as a pendulum. At the lowest point of its swing, the object has a kinetic energy of 10 J. Determine the speed of the object at the instant when the string makes an angle of 50° with the vertical.
Carly Brailer (Spring 2014)
 A 2.0 kg block slides down a frictionless incline from point A to point B. A force (magnitude P = 3.0 N) acts on the block between A and B, as shown. Points A and B are 2.0 m apart. If the kinetic energy of the block at A is 10 J, what is the kinetic energy of the block at B?
Zac Riley (Spring 2014)
 The two masses in the figure are released from rest. After the 3.0 kg mass has fallen 1.5 m, it is moving with a speed of 3.8 m/s. What is the change in mechanical energy done on the system during this time interval by the frictional force on the 2.0 kg mass?
Greg Sanda (Spring 2014)
 A 1.2kg mass is projected up a rough circular track (radius = 0.80 m) as shown. The speed of the mass at point A is 8.4 m/s, and at point B, it is 5.6 m/s. What is the change in mechanical energy between A and B caused by the force of friction?
Erik Butcher (Spring 2014)
 Two clowns are separately launched from the same springloaded circus cannon with the spring compressed the same distance each time. Clown A has a 40kg mass; clown B a 60kg mass. The relation between their speeds at the instant of launch is:
Mary Byrd Ewell (Spring 2014)
 A large spring is used to stop the cars after they come down the last hill of a roller coaster. The cars start at rest at the top of the hill and are caught by a mechanism at the instant their velocities at the bottom are zero. Compare the compression of the spring, x_{A}, for a fully loaded car with that, x_{B}, for a lightly loaded car when m_{A} = 2m_{B}.
Dani Monroe (Spring 2014)
 A 2.0 kg block slides down a plane (inclined at 40° with the horizontal) at a constant speed of 5.0 m/s. At what rate is the gravitational force on the block doing work?
Diamond Cherry (Spring 2014)
Angular Momentum
 A puck on a frictionless air hockey table has a mass of 5.0 kg and is attached to a cord passing through a hole in the surface as in the figure. The puck is revolving at a distance 2.0 m from the hole with an angular velocity of 3.0 rad/s. The angular momentum of the puck (in kg⋅m^{2}/s) is:
Katie Balardi (Spring 2014)
Universal Gravitation
 The period of a satellite circling planet Romulus is observed to be 84 s when it is in a circular orbit with a radius of 8.0 x 10^{6} m. What is the mass of planet Romulus?
Allison Leon (Spring 2014)
 What is the kinetic energy of a 200 kg satellite as it follows a circular orbit of radius 8.0 x 10^{6} m around the Earth? (Mass of Earth = 6.0 x 10^{24} kg.)
Victoria DeLuca (Spring 2014)
 Halley's comet moves about the sun in an elliptical orbit with its closest approach to the sun being 0.59 A.U. and its furthest distance being 35 A.U. [1 Astronomical Unit (A.U.) is the Earthsun distance or 1.5 x 10^{11} m.] If the comet's speed at closest approach is 54 km/s, what is its speed when it is farthest from the sun?
John Gonzalez (Spring 2014)
Static Equilibrium
 A horizontal uniform meter stick supported at the 50cm mark has a mass of 0.50 kg hanging from it at the 20 cm mark and a 0.30 kg mass hanging from it at the 60 cm mark. Determine the position on the meter stick at which one would hang a third mass of 0.60 kg to keep the meter stick balanced.
Samantha Zaveda (Spring 2014)
Elasticity
 A 20 m long steel wire (crosssection 1.0 cm^{2}, Young's modulus 2.0 × 10^{11} N/m^{2}), is subjected to a load of 25,000 N. How much will the wire stretch under the load?
Collin Preston (Spring 2014)
 A stonecutter's chisel has an edge area of 0.7 cm^{2}. If the chisel is struck with a force of 42 N, what is the pressure exerted on the stone?
Kurt Walker (Spring 2014)
 For safety in climbing, a mountaineer uses a 50 m long nylon rope that is 1.0 cm in diameter. When supporting a 90 kg climber, the rope elongates 1.6 m. Find the Young's modulus for the rope material.
Alex Eller (Spring 2014)
Fluid Mechanics
 A hydraulic lift raises a 2,000 kg automobile when a 500 N force is applied to the smaller piston. If the smaller piston has an area of 10 cm^{2}, what is the crosssectional area of the larger piston?
Madie Greer (Spring 2014)
