Question 1

A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve whose diameter is 0.20 km. What is the magnitude of the friction force required to keep the car from sliding?

Accepted Answer

$9000\ \mathrm{N}$

Question 2

A stone with mass $1.0\ \mathrm{kg}$ is tied to the end of a light string, which keeps it moving in a circle with a radius of $0.50\ \mathrm{m}$ at a perfectly smooth horizontal plane. If the stone makes one full rotation every $0.40\ \mathrm{s}$, what is the tension in the string?

Accepted Answer

$31.4\ \mathrm{N}$

Question 3

If the work done to stretch an ideal spring by $6.0\ \mathrm{m}$ is $7.5\ \mathrm{kJ}$, what is the spring constant (force constant) of this spring?

Accepted Answer

$7500\ \mathrm{N/m}$

Question 4

A $5.0\ \mathrm{kg}$ boy uses energy to run up a flight of stairs that is $10.0\ \mathrm{m}$ high. If he runs up in $8.0\ \mathrm{s}$, what is his average power output?

Accepted Answer

$735\ \mathrm{W}$

Question 5

An astronaut in an earth satellite feels weightless because:

Accepted Answer

The astronaut is falling.

Question 6

A $700\ \mathrm{m}$ radius space station rotates so that the astronaut standing inside experiences $1\ \mathrm{RPM}$. What is the minimum period $T$ in seconds?

Accepted Answer

$733\ \mathrm{s}$

Question 7

What is the radial acceleration on the astronaut standing inside the space station in terms of $g$ if the tangential speed is $7.68\ \mathrm{m/s}$ and the radius is $700\ \mathrm{m}$?

Accepted Answer

$0.783\ g$

Question 8

A car of mass $80\ \mathrm{kg}$ is released from rest at a height of $6.0\ \mathrm{m}$ above the bottom of a vertical loop of radius $20.0\ \mathrm{m}$. What is the speed of the car at the top of the loop?

Accepted Answer

$19.8\ \mathrm{m/s}$

Question 9

At the top of the loop, what is the normal force on the car if its mass is $80\ \mathrm{kg}$ and its speed is $19.8\ \mathrm{m/s}$?

Accepted Answer

$490\ \mathrm{N}$

Question 10

A $5.0\ \mathrm{kg}$ block slides up a $30^\circ$ incline with kinetic friction $\mu_k = 0.20$ between the block and the surface. If the block starts with a speed of $6.28\ \mathrm{m/s}$, how high above the ground does it travel up the incline?

Accepted Answer

$0.259\ \mathrm{m}$

Question 11

Two cars, each of mass $m$, collide head-on at $30\ \mathrm{mph}$ each. If the collision is perfectly inelastic, what is the final velocity of the combined mass?

Accepted Answer

$0\ \mathrm{mph}$

Question 12

A $5.0\ \mathrm{kg}$ block moving at $6.28\ \mathrm{m/s}$ collides with a stationary $7.0\ \mathrm{kg}$ block. If the collision is perfectly inelastic, what is the final velocity of the combined mass?

Accepted Answer

$2.62\ \mathrm{m/s}$

Question 13

A $5.0\ \mathrm{kg}$ block moving at $6.28\ \mathrm{m/s}$ collides with a stationary $7.0\ \mathrm{kg}$ block. What is the loss in mechanical energy due to the collision?

Accepted Answer

$57.4\ \mathrm{J}$

Question 14

A $5.0\ \mathrm{kg}$ block moving at $6.28\ \mathrm{m/s}$ collides with a stationary $7.0\ \mathrm{kg}$ block. What is the magnitude of the impulse delivered to the $7.0\ \mathrm{kg}$ block?

Accepted Answer

$610\ \mathrm{N \cdot s}$

Question 15

A $5.0\ \mathrm{kg}$ block slides up a $30^\circ$ incline with kinetic friction $\mu_k = 0.20$ and initial speed $6.28\ \mathrm{m/s}$. What is the work done by friction as the block travels up the incline for a distance $L$?

Accepted Answer

$W_f = -\mu_k m g \cos(30^\circ) L$

Question 16

A $5.0\ \mathrm{kg}$ block slides up a $30^\circ$ incline with kinetic friction $\mu_k = 0.20$ and initial speed $6.28\ \mathrm{m/s}$. What is the equation relating the initial kinetic energy, work done by friction, and the change in potential energy?

Accepted Answer

$KE_i + W_f = m g h$

Question 17

A $5.0\ \mathrm{kg}$ block slides up a $30^\circ$ incline with kinetic friction $\mu_k = 0.20$ and initial speed $6.28\ \mathrm{m/s}$. What is the vertical height $h$ reached by the block?

Accepted Answer

$0.259\ \mathrm{m}$

Question 18

If a space station is placed in a circular orbit around Earth at a distance of $5.00 	imes 10^6\ \mathrm{m}$ above the surface, what is the gravitational force on a $5000\ \mathrm{kg}$ astronaut inside?

Accepted Answer

$4.21 	imes 10^4\ \mathrm{N}$

exam two - exan 2 practice test

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