PHY 201 Reading Quizzes

6.10 Ryan uses a 20cm long wrench to tighten a nut, turning it clockwise. The wrench handle is tilted 30 degrees above the horizontal. Ryan pulls straight down on the end with a force of 100N. How much torque does Ryan exert on the nut?

(100N)(cos30)(0.2m)

10.9 When a spring is stretched by 5 cm, its elastic potential energy is 1 J. What will its elastic potential energy be if it is compressed by 10 cm?

-4J

6.3 The hand of a clock travels one quarter of the way around its circular path. What is the angular displacement in radians?

-pi/2 radians

6.8 A 1m long dumbbell has a 10kg mass on one end and a 5kg mass on the other. What is the location of the center of gravity of the dumbbell?

0.17m from the center of the dumbbell (CG = (x1m1+x2m2)/(m1+m2)

10.8 A spring with a spring constant of 4.0N/m is stretched from its equilibrium length to a length that is 0.30m longer than its equilibrium length. how much potential energy is stored in the spring?

0.18 Nm (PE = 1/2kx2)

6.5 An object has an initial angular position of 3 radians. It rotates to an angular position at 5 radians. If this occurs in a 4 second time interval, what is the average angular speed of the object?

0.5 rad/s (w= delta theta/delta t)

12.1 If the period of oscillation is 2 s. What is the frequency of oscillation?

1/2 Hz (f = 1/T)

9.9 A 0.2 kg ball has a velocity of +40 m/s in the horizontal direction and -30 m/s in the vertical direction. What is the magnitude of the balls momentum?

10 kg m/s (p=mv)

9.7 A 2 kg ball of clay traveling at 3 m/s to teh right hits a wall and sticks. The collision takes 0.5s. What is the average force of the wall on the clay during the collision?

12N (J = F x delta t)

8.5 A 1kg weight is suspended from a spring, stretching it by 5 cm. how much does the spring stretch if the 1kg weight is replaced by a 3kg weight?

15 cm (F=kx)

6.4 If an object moves in a circular path traveling through an angular displacement of 3 radians. If the circular path has a radius of 5 m, how long is the arc length of the object's path?

15m (s=r x theta)

1.4 What is the height of a tall person to the nearest meter?

2 m (hope this is the question they pick for the final)

8.10 A 10kg mass is hung from a 1 m long cable, causing the cable to stretch by 1mm. Suppose a 10 kg mass is hung from a 2m length of the same cable. How much does the cable stretch?

2 mm

6.11 A rotating sphere speeds up from its initial angular velocity of 3 rad/s to 7 rad/s in 2 s. what is the angular acceleration of the sphere during this interval?

2 rad/s2 (alpha = delta w/ delta t)

12.8 A ball is hung from a rope, making a pendulum. When it is pulled 5 degrees to the side, the restoring force is 1.0N. What will be the magnitude of the restoring force if the ball is pulled 10 degrees to the side?

2.0N

10.10 A block with an initial kinetic energy of 4.0J comes to rest after sliding 1.0m. How far would the block slide if it had 8.0J of initial kinetic energy?

2.0m

6.1 A car goes around a circular track in a time of 314 s. If the radius of the track is 1000 m, the average speed of the car is

20 m/s (v=(2piR)/t)

6.6 A disk with a diameter of 12 cm rotates about its center with an angular speed of 7 rad/s. What is the speed (in cm/s) of a point on the disk that is 3 cm from the axis of rotation?

21 cm/s (v=wr)

11.5 If you are of average weight, walking up a typical flight of stairs increases your body's potential energy by about 1800J. to accomplish this your body uses about 7200J of energy. The efficiency of this action is about

25% (eff = get/pay)

9.4 2000 kg car going to the right at 8 m/s 4000 kg car going to the left at 1 m/s then 2000 kg car going to the left at 4 m/s v of 4000 kg car?

3 m/s to the right

1.3 Janet starts from her house to take a stroll in her neighborhood. After walking for 1.5 hours she has walked 6.0 miles and is 4.5 miles from home. What was her average speed?

4 mph (speed=distance/time)

8.4 The end of a spring is pulled to the right by 4 cm; the restoring force is 8N to the left. If the spring is returned to the equilibrium position and then pushed to teh left by 2 cm, the restoring force is

4N to the right

11.2 How many joules of energy does a 100W light bulb require to operate for 5s?

500J (P=W/delta t)

10.3 An object initially at rest experiences a net force of 2.0N as it is moved 3.0m in the same direction as the force. How much work was done on the object as it was moved 3m?

6.0 Nm (W=Fx)

9.6 A 2 kg ball traveling 3 m/s to the right hits a wall and sticks. The collision takes 0.5s. What is the magnitude of the impulse imparted on the clay?

6.0 kg m/s

10.1 Disk has a moment of inertia of 2.0 kgm2. it rotates at a speed of 3.0 rad/s. What is the angular momentum?

6.0 kgm2/s (L=Iw)

10.7 A 2 kg object initially at the surface of the earth is raised to a height of 3m. What is the increase in gravitational potential energy as the object is raised to 3m?

60Nm (PE=mgh)

11.3 Four student run up a flight of stairs. Which student has the greatest power output? 80 kg, 10s 80 kg, 8s 64 kg, 8s All the same

80 kg, 8 s

10.2 Disk has a moment of inertia of 2.0 kgm2. It rotates at a speed of 3.0 rad/s. What is the rotational energy of the disk?

9.0 kgm2/s2 (K=1/2Iw2)

10.6 A 2.0kg object is moving at constant speed of 3.0 m/s. What is the kinetic energy of the object?

9.0 kgm2/s2 (KE = 1/2mv2)

1.8 Approximating pi as the number 3, what is the area of a circle of radius 2?

A=pi(r^2)=12

2.4 Plot of velocity versus time graph. At which point does the object have the greatest instantaneous positive acceleration?

Acceleration = slope

8.2 Static equilibrium calculations

Allow you to choose the pivot point

5.7 The force of kinetic friction is...

Always equal to the coefficient of kinetic friction times the normal force on the object

5.6 The force of rolling friction is...

Always equal to the coefficient of rolling friction times the normal force on the object

5.4 The normal force on an object...

Always points perpendicular to the surface that it is touching

12.6 Damped oscillations result in

An amplitude that decreases exponentially

12.9 When you run, your gait is more rapid. To decrease the period of the pendulum motion in your arms to match, you should

Bend them at the elbows (shortening their effective length)

11.8 Crane 1 uses 10 kJ of energy to lift a 50 kg box. Crane 2 uses 20 kJ to life a 100 kg box the same distant. Which crane is more efficient?

Both

12.5 The total energy of a mass-spring oscillator is given by

Both 1/2kA2 and 1/2mvmax2

9.1 A 3 kg object moves to the right at 5 m/s and a 5 kg object move at 3 m/s to the right. Which object has the largest momentum?

Both objects have the same momentum (p=mv)

12.4 The maximum velocity of a simple harmonic oscillator depends on

Both the frequency and the amplitude of the oscillation

11.10 What is the largest unit of energy?

Calorie (food Cal)

9.3 Same cars going towards wall. One sticks, one bounces back at 4 m/s. In which case is the magnitude of impulse imparted on the car greater?

Case 2 (bounce back)

11.4 Power can be expressed as

Change in energy divided by change in time Work done divided by change in time Force times velocity

5.5 The force of static friction is...

Changes depending on how much a stationary object is pushed or pulled

5.3 The apparent weight of an object is...

Dependent on the acceleration of the object

4.11 A 50,000kg airplane accelerates from rest to 80 m/s as it travels along a runway in 40s. What is the net force on the airplane?

F = 100,000N

5.2 calculate the gravitational force on earth for an object that has a mass of 2kg

F = 19.6N

1.1 Know motion diagrams

Getting closer together: slowing down Same distance: constant velocity Getting farther apart: speeding up

4.7 A basketball is falling in a strong breeze. Identify two forces being exerted on the basketball and directions.

Gravity (down) Wind (direction of wind)

7.4 Consider a planet that has twice the mass and same radius as the earth. The gravitational force on a 1kg object on the surface of that planet will be

Greater than on earth

1.7 Right triangle Side 1 = 3 Side 2 = 4 Hypotenuse = ?

H = 5

9.8 Force versus time graph, be able to find the impulse

Impulse = area under the curve

11.1 Identify the true statement.

In a perfectly elastic collision both momentum and energy are conserved

11.9 Identify the true statement

In a perfectly inelastic collision moment is conserved by energy is not

12.7 When the position of an object in simple harmonic motion is in the positive direction, its acceleration is

In the negative direction

8.8 The tensile strength

Is the largest stress that a material can sustain before breaking

8.9 The elastic limit

Is the maximum stretch an object can sustain before becoming permanently deformed

8.7 Yong's modulus

Is the proportionality constant between stress and strain

7.5 Consider a planet that has same mass and twice the radius of earth. The gravitational force on a 1 kg object on the surface of that planet would be

Less than on earth

7.6 Consider a planet that has twice the mass and twice the radius of the earth. the gravitational force on a 1 kg object on the surface of that planet will be

Less than on earth

11.7 A 40 kg tiber wolf uses approximately 19,000 kJ during the course of a day. A Komodo dragon, 40 kg, only uses 2100 kJ. This can be explained because

Mammals use energy to maintain a constant body temperature

5.1 Identify the false statement

No forces act on an object that is in equilbrium

2.10 An airplane on a runway accelerates a 2 m/s2 a) How much time does it take for the plane to reach its take-off speed of 80 m/s? b) How far does the plane travel along the runway in that time?

Once again I don't have the answer.

1.9 Triangle Sides = 12, 5, 13 Be able to find sin, cos, tan

SOHCAHTOA

2.8 A springbok leaps by extending its legs forcefully, accelerating at 30 m/s2 over a distance of 0.6 m. What is its speed just after it leaves the ground?

Slacking. Don't know the answer.

2.9 A rock is dropped from a height of 19.6 m. If air resistance can be ignored, how long does it take for the rock to hit the ground?

Sorry don't have a an answer for this one. Will work out and get back to everyone.

4.8 A single 2N force acts on a 4kg block. A single 4N force acts on a 2kg block. Identify the true statement

The acceleration of the 2 kg block is quadruple the acceleration of the 4 kg block

7.3 The r in Newton's Law of Gravity refers to

The distance between the centers of the objects being attracted

12.10 Resonance occurs when

The driving frequency is equal to the natural frequency of the oscillating object

4.10 Newton's third law is concerned with action-reaction pairs. Consider a car accelerating along a highway. Which of the following is an appropriate pair of forces showing Newton's third law?

The friction force of the road on the car's tires and the frictional force of the car's tires on the road

6.7 The ability of a force to cause rotation depends on...

The magnitude of the force The distance from the pivot to the point at which the force is applied The angle at which the force is applied

3.2 There is an acceleration whenever...

The magnitude of the velocity vector changes There is a change in speed The direction of the velocity vector changes

12.3 The period of a mass-spring system depends on:

The mass that is oscillating and the amplitude of the oscillation

8.1 Static equilibrium requires all of the following except

The net center of gravity is zero (Fx net, Fy net, and torque net = 0)

6.2 For a car driving with a constant speed at the bottom on a circular dip in the road...

The normal force is greater than the for of gravity on the car

5.10 Consider the same object on the earth and the moon.

The object has the same mass but different weight

8.3 As long as the object's center of gravity remains over the base of support

The object is said to be stable

12.2 The period of a pendulum depends on

The pendulum's length and the acceleration due to gravity

7.1 The period of a satellite's orbit depends on

The radius of the satellite's orbit

7.2 weightlessness occurs because

The spacecraft and everything in it are falling together

7.7 Identify the true statement

The square of the period of an orbit is proportional to the cube of the radius of the orbit

5.9 Identify the false statement about massless ropes and strings and massless pulleys

The tension in a rope is equal to the sum of the forces pulling at each end

5.8 Case A: A man pulls on a rope with a force of 100N Case B: Two men pull on opposite ends of a rope, each with a force of 100N

The tension in the rope in both cases is 100N

4.4 A small car drives into a large truck. Identify the true statement.

The two forces are equal in magnitude

4.5 If an elevator is accelerating upward...

The upward force of the cable = the downward force of gravity

4.6 If an elevator is moving upward and slowing to a stop...

The upward force of the cable = the downward force of gravity

4.9 Identify the true statement

The vector sum of all of the forces acting on an object is always in the same direction as the objects acceleration

9.2 A 3 kg object accelerates to the left at 5 m/s2 and a 5 kg object accelerates at 3 m/s2 to the right. Which object has the largest momentum?

There is not enough information

4.2 A frog is resting on a slope. What can be said about the friction force acting on the front?

There is static friction directed up the slope

11.6 A runner is moving at a constant speed on level ground. Chemical energy in the runner's body is being transformed into other forms of energy. Most of the chemical energy is transformed into

Thermal energy (about 75%)

1.5 Know how to add vectors

Tip to tail

3.1 For the two vectors shown, what is the sum of vector A and B?

Tip to tail

6.9 A ball on the end of a string swings in a horizontal circle once every second. State whether the magnitude of each of the following quantities is zero, constant (but not zero) or changing

Velocity: constant Angular velocity: constant Centripetal acceleration: constant Angular acceleration: zero Tangential acceleration: zero

9.5 A 1000 kg car traveling at 20 m/s collides with a stationary 3000 kg truck. After collision they stick together. Vf?

Vf = 5.0 m/s (pi = pf)

4.3 A rocket-propelled car has a thrust force pushing it forward along a level track. A frictional force and a drag force are both pushing it backward. Identify two other forces acting on the car (with directions of forces)

Weight (down) Normal (up)

4.1 A skier is being towed up a snow-covered hill. Identify four forces that are being exerted on the skier. In what direction do each of these forces act?

Weight (down) Tension (direction of rope) Normal (perpendicular to slope) Friction (direction of movement)

8.6 A solid metal rod..

Will have a restoring force that is proportional to the amount it is stretched

10.4 An object initially at rest experiences a net force of 2.0N as it is moved 3.0m in the same direction as the force. What is the final kinetic energy?

Zero

10.5 A 2.0kg object is moving at 3.0 m/s as a force of 5.0N is applied perpendicular to the direction that it is moving. How much work is done as the object moves 3m?

Zero

1.2 Bill is standing 5 m east of 30th and Dodge. He then walks to a position 23 m east of 30th and Dodge. a) Magnitude and direction of displacement? b) If he does this in 2 s, what is his speed? c) If he does this in 3 s, magnitude and direction of his velocity?

a) +18 m b) 9 m/s c) +6 m/s

2.6 An object is dropped. If one could neglect air resistance... a) What would be its velocity after 1 s? b) What would be its displacement after 1 s?

a) -9.8 m/s2 b) -4.9 m

2.5 A car accelerates at 0.5 m/s2 starting from rest. a) After 3 s what is its velocity b) After 3 s how far has ti traveled from its starting position?

a) 1.5 m/s b) 2.25 m

1.6 a) Express as an integer 4^2(2^-1) b) Express as a decimal number (3 x 10^3)(2 x 10^-5)

a) 8 b) 0.06

2.3 Consider the graph below to be a plot of position vs. time. At which point does the object have the greatest instantaneous velocity?

a) Velocity = slope

1.10 a) Right triangle sin(x) = 0.6 cos(x) = 0.8 tan(x) = ? b) Hypotenuse = 10, what is the length of the side that makes the angle (x)?

a) tan(x) = 0.6/0.8 b) 1

2.7 The figure shows a velocity versus time graph of a ball thrown straight upward. Assuming g=-10 and no air resistance a) ball's velocity when it is at the top of it's path? b) ball's acceleration when it is at the top of it's path? c) Ball's speed when launched is 30 m/s. What is the ball's speed just before it hits the ground? t = 6s

a) v = 0 m/s b) a = -10 m/s2 c) v = -30 m/s

3.3 Two velocity vectors. Find the change in velocity

delta v = vf - vi delta v = vf + -vi

2.2 Know to get position from a velocity versus time graph

position = area under the curve

1.11 sin(90) = ? tan(0) = ? cos(180) = ?

sin(90) = 1 tan(0) = 0 cos(180) = -1

2.1 Know how to get velocity from a position versus time graph

velocity = slope