Question 1

A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g cart. What is the speed of the 320-g cart just after the collision?

Accepted Answer

A)  0.68 m/s 
B)  0.11 m/s 
C)  0.21 m/s 
D)  1.4 m/s 
E)  1.1 m/s 
A)  0.68 m/s 
B)  0.11 m/s 
C)  0.21 m/s 
D)  1.4 m/s 
E)  1.1 m/s

Question 2

In a ballistics test, a 28-g bullet pierces a sand bag that is 30${~cm}$ thick. If the initial bullet velocity was 55${~m} / \mathrm { s }$ and it emerged from the sandbag moving at 18${~m} / \mathrm { s } \text {, }$ what was the magnitude of the friction force (assuming it to be constant) that the bullet experienced while it traveled through the bag?

Accepted Answer

A)  130 N 
B)  38 N 
C)  13 N 
D)  1.3 N 
A)  130 N 
B)  38 N 
C)  13 N 
D)  1.3 N

Question 3

How high a hill would a 75-kg hiker have to climb to increase her gravitational potential energy by 10,000 J?

Accepted Answer

The answer of How high a hill would a 75-kg...

Question 4

Consider a solid uniform sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?

Accepted Answer

A)  Translational kinetic energy is larger. 
B)  Rotational kinetic energy is larger. 
C)  Both are equal. 
D)  You need to know the speed of the sphere to tell. 
A)  Translational kinetic energy is larger. 
B)  Rotational kinetic energy is larger. 
C)  Both are equal. 
D)  You need to know the speed of the sphere to tell.

Question 5

When a car of mass 1167 ${~kg}$ accelerates from 10.0 m/s to some final speed, 4.00 × 105 J of work are done. Find this final speed.

Accepted Answer

A)  28.0 m/s 
B)  22.4 m/s 
C)  25.2 m/s 
D)  30.8 m/s 
A)  28.0 m/s 
B)  22.4 m/s 
C)  25.2 m/s 
D)  30.8 m/s

Question 6

A girl throws a stone from a bridge. Consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case. 
Case A: Thrown straight up.
Case B: Thrown straight down.
Case C: Thrown out at an angle of 45° above horizontal.
Case D: Thrown straight out horizontally.
In which case will the speed of the stone be greatest when it hits the water below if there is no significant air resistance?

Accepted Answer

A)  Case A 
B)  Case B 
C)  Case C 
D)  Case D 
E)  The speed will be the same in all cases. 
A)  Case A 
B)  Case B 
C)  Case C 
D)  Case D 
E)  The speed will be the same in all cases.

Question 7

What is the net power needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s in 4.00 seconds?

Accepted Answer

A)  100 kW 
B)  10.0 kW 
C)  140 kW 
D)  14.0 kW 
E)  275 kW 
A)  100 kW 
B)  10.0 kW 
C)  140 kW 
D)  14.0 kW 
E)  275 kW

Question 8

A solid uniform ball with a mass of 125 g is rolling without slipping along the horizontal surface of a table with a speed of 4.5 m/s when it rolls off the edge and falls towards the floor, 1.1 m below. What is the rotational kinetic energy of the ball just before it hits the floor?

Accepted Answer

A)  0.51 J 
B)  0.73 J 
C)  1.1 J 
D)  2.6 J 
E)  This question cannot be answered without knowing the radius of the ball. 
A)  0.51 J 
B)  0.73 J 
C)  1.1 J 
D)  2.6 J 
E)  This question cannot be answered without knowing the radius of the ball.

Question 9

How much work must be done by frictional forces in slowing a 1000-kg car from $26.1 \mathrm {~m} / \mathrm { s }$ to rest?

Accepted Answer

A)  3.41 × 105 J 
B)  2.73 × 105 J 
C)  4.09 × 105 J 
D)  4.77 × 105 J 
A)  3.41 × 105 J 
B)  2.73 × 105 J 
C)  4.09 × 105 J 
D)  4.77 × 105 J

Question 10

A disk and a hoop of the same mass and radius are released at the same time at the top of an inclined plane. If both are uniform, which one reaches the bottom of the incline first if there is no slipping?

Accepted Answer

A)  The hoop 
B)  The disk 
C)  Both reach the bottom at the same time. 
A)  The hoop 
B)  The disk 
C)  Both reach the bottom at the same time.

Question 11

A solid uniform disk is rolling without slipping along a horizontal surface with a speed of 4.5 m/s when it starts up a ramp that makes an angle of 25° with the horizontal. What is the speed of the disk after it has rolled 3.0 m up as measured along the surface of the ramp?

Accepted Answer

A)  4.0 m/s 
B)  1.9 m/s 
C)  2.1 m/s 
D)  6.8 m/s 
E)  8.0 m/s 
A)  4.0 m/s 
B)  1.9 m/s 
C)  2.1 m/s 
D)  6.8 m/s 
E)  8.0 m/s

Question 12

In a certain nuclear reactor, neutrons suddenly collide with deuterons, which have twice the mass of neutrons. In a head-on elastic collision with a stationary deuteron, what fraction of the initial kinetic energy of a neutron is transferred to the deuteron?

Accepted Answer

A)  1/2 
B)  1/3 
C)  3/4 
D)  5/6 
E)  8/9 
A)  1/2 
B)  1/3 
C)  3/4 
D)  5/6 
E)  8/9

Question 13

As shown in the figure, two blocks are connected by a light string that passes over a frictionless pulley having a moment of inertia of 0.0040 kg ∙ m2 and diameter 10 cm. The coefficient of kinetic friction between the table top and the upper block is 0.30. The blocks are released from rest, and the string does not slip on the pulley. How fast is the upper block moving when the lower one has fallen 0.60 m?

Accepted Answer

A)  1.2 m/s 
B)  5.4 m/s 
C)  3.2 m/s 
D)  2.0 m/s 
E)  1.4 m/s 
A)  1.2 m/s 
B)  5.4 m/s 
C)  3.2 m/s 
D)  2.0 m/s 
E)  1.4 m/s

Question 14

In a perfectly elastic collision, a 400-g ball moving toward the east at 3.7 m/s suddenly collides head-on with a 200 g ball sitting at rest.
(a) Determine the velocity of the first ball just after the collision.
(b) Determine the velocity of the second ball just after the collision.
(c) Is kinetic energy conserved in this collision? How do you know?

Accepted Answer

(a) 1.2 m/s toward t

Question 15

While spinning down from 500 rpm to rest, a flywheel does $3.9 \mathrm {~kJ}$ of work. This flywheel is in the shape of a solid uniform disk of radius 1.2 m. What is the mass of this flywheel?

Accepted Answer

A)  4.0 kg 
B)  3.4 kg 
C)  4.6 kg 
D)  5.2 kg 
A)  4.0 kg 
B)  3.4 kg 
C)  4.6 kg 
D)  5.2 kg

Question 16

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 106 N/m. What is the maximum distance the spring compresses?

Accepted Answer

A)  0.17 m 
B)  0.34 m 
C)  0.51 m 
D)  0.68 m 
A)  0.17 m 
B)  0.34 m 
C)  0.51 m 
D)  0.68 m

Question 17

An ideal spring has a spring constant (force constant) of 60 N/m. How much energy does it store when it is stretched by 1.0 cm?

Accepted Answer

A)  0.0030 J 
B)  0.30 J 
C)  60 J 
D)  600 J 
A)  0.0030 J 
B)  0.30 J 
C)  60 J 
D)  600 J

Question 18

Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?

Accepted Answer

A)  The 500-kg object 
B)  The 1000-kg object 
C)  Both have the same kinetic energy. 
A)  The 500-kg object 
B)  The 1000-kg object 
C)  Both have the same kinetic energy.

Question 19

A 10-kg dog is runnng with a speed of 5.0 m/s. What is the minimum work required to stop the dog in 2.40 s?

Accepted Answer

A)  50 J 
B)  75 J 
C)  100 J 
D)  125 J 
A)  50 J 
B)  75 J 
C)  100 J 
D)  125 J

Question 20

A rock falls from a vertical cliff that is 4.0 m tall and experiences no significant air resistance as it falls. At what speed will its gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy?

Accepted Answer

A)  3.1 m/s 
B)  4.4 m/s 
C)  6.3 m/s 
D)  8.9 m/s 
E)  13 m/s 
A)  3.1 m/s 
B)  4.4 m/s 
C)  6.3 m/s 
D)  8.9 m/s 
E)  13 m/s

Exam 10: Energy and Work

A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g cart. What is the speed of the 320-g cart just after the collision?

How high a hill would a 75-kg hiker have to climb to increase her gravitational potential energy by 10,000 J?

Consider a solid uniform sphere of radius R and mass M rolling without slipping. Which form of its kinetic energy is larger, translational or rotational?

When a car of mass 1167 kg{~kg} kg accelerates from 10.0 m/s to some final speed, 4.00 × 105 J of work are done. Find this final speed.

What is the net power needed to change the speed of a 1600-kg sport utility vehicle from 15.0 m/s to 40.0 m/s in 4.00 seconds?

A solid uniform ball with a mass of 125 g is rolling without slipping along the horizontal surface of a table with a speed of 4.5 m/s when it rolls off the edge and falls towards the floor, 1.1 m below. What is the rotational kinetic energy of the ball just before it hits the floor?

How much work must be done by frictional forces in slowing a 1000-kg car from 26.1 m/s26.1 \mathrm {~m} / \mathrm { s }26.1 m/s to rest?

A disk and a hoop of the same mass and radius are released at the same time at the top of an inclined plane. If both are uniform, which one reaches the bottom of the incline first if there is no slipping?

A solid uniform disk is rolling without slipping along a horizontal surface with a speed of 4.5 m/s when it starts up a ramp that makes an angle of 25° with the horizontal. What is the speed of the disk after it has rolled 3.0 m up as measured along the surface of the ramp?

In a certain nuclear reactor, neutrons suddenly collide with deuterons, which have twice the mass of neutrons. In a head-on elastic collision with a stationary deuteron, what fraction of the initial kinetic energy of a neutron is transferred to the deuteron?

While spinning down from 500 rpm to rest, a flywheel does 3.9 kJ3.9 \mathrm {~kJ}3.9 kJ of work. This flywheel is in the shape of a solid uniform disk of radius 1.2 m. What is the mass of this flywheel?

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 106 N/m. What is the maximum distance the spring compresses?

An ideal spring has a spring constant (force constant) of 60 N/m. How much energy does it store when it is stretched by 1.0 cm?

Which one has larger kinetic energy: a 500-kg object moving at 40 m/s or a 1000-kg object moving at 20 m/s?

A 10-kg dog is runnng with a speed of 5.0 m/s. What is the minimum work required to stop the dog in 2.40 s?

A rock falls from a vertical cliff that is 4.0 m tall and experiences no significant air resistance as it falls. At what speed will its gravitational potential energy (relative to the base of the cliff) be equal to its kinetic energy?

Representing Motion

Motion in One Dimension

Vectors and Motion in Two Dimensions

Forces and Newtons Laws of Motion

Applying Newtons Laws

Gravity

Rotational Motion

Equilibrium Ad Elasticity

Momentum

Using Energy

Thermal Properties of Matter

Fluids

Oscillations

Traveling Waves and Sound

Superposition and Standing Waves

Wave Optics

Ray Optics

Optical Instruments

Electric Fields and Forces

Electric Potential

Current and Resistance

Circuits

Magnetic Fields and Forces

EM Induction and Em Waves

AC Electricity

Relativity

Quantum Physics

Atoms and Molecules

Nuclear Physics

Filters

When a car of mass 1167 ${~kg}$ accelerates from 10.0 m/s to some final speed, 4.00 × 10⁵ J of work are done. Find this final speed.

How much work must be done by frictional forces in slowing a 1000-kg car from $26.1 \mathrm {~m} / \mathrm { s }$ to rest?

While spinning down from 500 rpm to rest, a flywheel does $3.9 \mathrm {~kJ}$ of work. This flywheel is in the shape of a solid uniform disk of radius 1.2 m. What is the mass of this flywheel?

A 1500-kg car moving at 25 m/s hits an initially uncompressed horizontal ideal spring with spring constant (force constant) of 2.0 × 10⁶ N/m. What is the maximum distance the spring compresses?