PHY 110 Final

An object has a velocity of (5.4 m/s)i-(4.8m/s)j. Over a period of 1.3 s, its velocity changes to (1.7 m/s)i+(5.9 m/s)j. What is its acceleration?

(-2.8m/s^2)i+(8.2m/s^2)j

Let A=(2m)i+(6m)j-(3m)k and B=(4m)i+(2m)j+(1m)k. What is the vector sum A+B? What is the vector difference A-B? What is the dot product A*B?

(6m)i+(8m)j-(2m)k (-2m)i+(4m)j-(4m)k 17

Starting at time t=0, an object moves along a straight line with velocity in m/s given by v(t)=98-2t^2, where t is in seconds. What is its acceleration when it momentarily stops?

-28 m/s^2

Two space people are floating together with zero speed in a gravity-free region of space. The mass of spacewoman A is 120 kg and that of spaceman B is 90 kg. Spacewoman A pushes B away from her with B attaining a final speed of 0.5 m/s. What is the final recoil speed of Spacewoman A?

.375 m/s

A car travels east at constant velocity. What is the net force on the car?

0

If two vectors are perpendicular to each other, what is their dot product?

0

Blocks A and B are moving toward each other along the x axis. A has a mass of 2.0 kg and a velocity of 50 m/s, while B has a mass of 4.0 kg and a velocity of -25 m/s. They suffer an elastic collision and move off along the x axis. What is the kinetic energy transferred from A to B during the collision

0 J

A disk with a rotational inertia of 2.0 kg*m^2 and a radius of 0.40 m rotates on a frictionless fixed axis perpendicular to the disk faces and through its center. A force of 5.0 N is applied tangentially to the rim. What is the angular acceleration of the disk?

1 rad/s^2

The coordinate of a particle in meters is given by x(t)=16t-3.0t^3, where the time t is in seconds. The particle is momentarily at rest when t=?

1.3 s

Two automobiles are 150 kilometers apart and traveling toward each other. One automobile is moving at 60 km/hr and the other is moving at 40 km/hr. In how many hours will they meet?

1.5 hrs

A 0.20 kg particle moves along the x axis under the influence of a conservative force. The potential energy is given by U(x) = (8.0 J/m^2)x^2 + (2.0 J/m^4)x^4, where x is in coordinate of the particle. If the particle has a speed of 5.0 m/s when it is at x = 1.0 m, what is its speed when it is at the origin?

11 m/s

A 40N crate rests on a rough horizontal floor. A 12N horizontal force is then applied to it. If the coefficients of friction are us=0.5 and uk=0.4, give the magnitude of the frictional force on the crate

12N

A wheel of radius 0.5 m rolls without sliding on a horizontal surface as shown. Starting from rest, the wheel moves with constant angular acceleration 6 rad/s^2. What is the distance traveled by the center of the wheel from t=0 to t=3 s?

13.5 m

An object is released from rest. How far does it fall during the second second of its fall?

14.7 m

For a biological sample in a 1.0m radius centrifuge to have a centripetal acceleration of 25g what must its speed be?

15.7 m/s

A wheel of diameter 3.0 cm has a 4.0 m cord wrapped around its periphery. Starting from rest, the wheel is given a constant angular acceleration of 2 rad/s^2. How much time does it take for the cord to completely unwind?

16.3 s

A pulley with a radius of 3.0 cm and a rotational inertia of 4.5 x 10^-3 kg*m^2 is suspended from the ceiling. A rope passes over it with a 2.0 kg block attached to one end and a 4.0 kg block attached to the other. The rope does not slip on the pulley. When the velocity of the heavier block is 2.0 m/s, what is the total kinetic energy of the pulley and blocks?

22.01 J

A 0.2 kg stone is attached to a string and swung in a circle of radius 0.6 m on a horizontal and frictionless surface. If the stone makes 150 revolutions per minute, what is the tension force of the string on the stone?

29.6 N

The angular velocity of a rotating wheel increases 2 rev/s every minute. What is the angular acceleration of this wheel?

2pi/30 rad/s^2

A stone is tied to a 0.50m string and whirled at a constant speed of 4.0 m/s in a vertical circle. What is the acceleration at the bottom of the circle? Give both magnitude and direction.

32 m/s^2 upward

A boat is able to move through still water at 20 m/s. It makes a round trip to a town 3.0 km upstream. If the river flows at 5 m/s, what is the time required for this round trip?

320 s

Camping equipment weighing 6000N is pulled across a frozen lake by means of a horizontal rope. The coefficient of kinetic friction is 0.05. What is the work done by the campers in pulling the equipment 1000m at constant velocity? What is the work done by the campers in pulling the equipment 1000m if its speed is increasing at the constant rate of 0.20 m/s^2?

3x10^5 J 4.2x10^5 J

A baseball is hit straight up and is caught by the catcher 2.0 s later, at the same height at which it left the bat. What is the maximum height the ball reaches?

4.9 m

A monkey on the edge of a vertical cliff 20m high throws a stone horizontally outwards with a speed of 20m/s. It strikes the ground at what horizontal distance from the foot of the cliff?

40m

An 8000N car is traveling at 12m/s along a horizontal road when the brakes are applied. The car skids to a stop in 4.0 s. How much kinetic energy does the car lose in this time?

5.9x10^4 J

A robot pulls a 100N crate up a frictionless 30 degree slope 5m high as shown. Assuming that the crate moves at constant speed, what is the work done by the robot?

500 N-m

A simple pendulum consists of a 2.0 kg mass attached to a string. It is released from rest at X as shown. What is its speed at the lowest point Y?

6.02 m/s

A car moving with an initial velocity of 25 m/s north has a constant acceleration of 3 m/s^2 south. After 6 seconds what will its velocity be?

7 m/s north

A 90 kg man stands in an elevator that is moving up at a constant speed of 5.0 m/s. The force exerted by him on the floor is about how much?

882 N

At the same instant that a 0.50 kg ball is dropped from 25 m above Earth, a second ball, with a mass of 0.25 kg, is thrown straight upward from Earth's surface with an initial speed of 15 m/s. They move along nearby lines and pass without colliding. At the end of 2.0 s what is the acceleration of the center of mass of the two-ball system?

9.8 m/s^2 or 1g

An escalator is used to move 20 people (60 kg each) per minute from the first floor of a mall to the second floor, 5 m above. What is the power required to do this?

980 W

Three books (X,Y, and Z) rest on a table. The weight of each book is indicated. What is the force of book Z on book Y?

9N

A block of mass m is pulled at constant velocity along a rough horizontal floor by an applied force T as shown. What is the magnitude of frictional force? What is the vertical component of the force exerted on the block by the floor?

Fsk = Ftcosx Fn = mg-Ftsinx

Which of the following five coordinate versus time graphs represent the motion of an object moving with a constant nonzero speed?

II

A stone is dropped from a cliff. The graph that best represents its motion while it falls is

III

Which of the following five acceleration versus time graphs is correct for an object moving in a straight line at a constant velocity of 20 m/s?

V

During a short interval of time the speed v in m/s of an automobile is given by v=at^2+bt^3, where the time t is in seconds. What are the units of a and b respectively?

m/s^3 and m/s^4