Q: A 1200 kg car rounds a flat curve of radius $90.0\ \mathrm{m}$ with a coefficient of friction $\mu = 0.65$. What is the maximum speed the car can have without skidding?

$v_{\text{max}} = \sqrt{\mu g r}$

Q: A force $\vec{F} = (100\hat{i} + 9.0\hat{j} + 120\hat{k})\ \mathrm{kN}$ acts on an object displaced by $\vec{d} = (5.0\hat{i} + 4.0\hat{j})\ \mathrm{m}$. What is the work done by the force?

$W = \vec{F} \cdot \vec{d} = 100 \times 5.0 + 9.0 \times 4.0 = 500 + 36 = 536\ \mathrm{kJ}$

Q: Which equation best represents the conservation of mechanical energy for a system with friction?

$K_i + U_i = K_f + U_f + E_{\text{thermal}}$

Question 1

Which of the following is a correct example of a non-conservative force?

Accepted Answer

Frictional force

Question 2

A block of mass $m = 7\ \mathrm{kg}$ slides down a frictionless plane inclined at $	heta = 22^\circ$ to the horizontal. What is the acceleration of the block?

Accepted Answer

$a = g \sin 22^\circ$

Question 3

Which of Newton's laws explains why passengers move forward when a car suddenly stops?

Accepted Answer

Newton's First Law (Law of Inertia)

Question 4

A 1200 kg car rounds a flat curve of radius $90.0\ \mathrm{m}$ with a coefficient of friction $\mu = 0.65$. What is the maximum speed the car can have without skidding?

Accepted Answer

$v_{	ext{max}} = \sqrt{\mu g r}$

Question 5

A child of mass $22.5\ \mathrm{kg}$ sits $1.40\ \mathrm{m}$ from the center of a merry-go-round moving at $1.30\ \mathrm{m/s}$. What is the net horizontal force exerted on the child?

Accepted Answer

$F = m \dfrac{v^2}{r}$

Question 6

Two satellites orbit Earth at altitudes of $8500\ \mathrm{km}$ and $7000\ \mathrm{km}$ above the surface. Which satellite moves faster and by what factor?

Accepted Answer

The satellite at $7000\ \mathrm{km}$ moves faster by a factor $\sqrt{\dfrac{r_2}{r_1}}$

Question 7

Which of the following is NOT a fundamental force recognized by modern physics?

Accepted Answer

Friction

Question 8

A force $\vec{F} = (100\hat{i} + 9.0\hat{j} + 120\hat{k})\ \mathrm{kN}$ acts on an object displaced by $\vec{d} = (5.0\hat{i} + 4.0\hat{j})\ \mathrm{m}$. What is the work done by the force?

Accepted Answer

$W = \vec{F} \cdot \vec{d} = 100 	imes 5.0 + 9.0 	imes 4.0 = 500 + 36 = 536\ \mathrm{kJ}$

Question 9

A vertical spring with $k = 875\ \mathrm{N/m}$ is compressed $0.220\ \mathrm{m}$ by a $0.380\ \mathrm{kg}$ ball. What is the upward speed of the ball when released?

Accepted Answer

$v = \sqrt{\dfrac{k x^2}{m}}$

Question 10

Which equation best represents the conservation of mechanical energy for a system with friction?

Accepted Answer

$K_i + U_i = K_f + U_f + E_{	ext{thermal}}$

Question 11

An $80\ \mathrm{kg}$ mass is $1.5\ \mathrm{m}$ above the ground and compresses a spring $0.1\ \mathrm{m}$ with $k = 5.2\ \mathrm{kN/m}$. What is the total potential energy?

Accepted Answer

$U = mgh + \dfrac{1}{2} k x^2$

Question 12

A NASA satellite observes an asteroid of mass $4 	imes 10^9\ \mathrm{kg}$ approaching Earth at $660\ \mathrm{m/s}$ from $5.0 	imes 10^8\ \mathrm{km}$ away. Neglecting atmospheric friction, what principle is used to determine its impact speed?

Accepted Answer

Conservation of energy: $K_i + U_i = K_f + U_f$

Question 13

What is the escape velocity from Earth, given by the formula $v_{	ext{esc}} = \sqrt{\dfrac{2GM}{R}}$? What does $G$ represent?

Accepted Answer

$G$ is the universal gravitational constant

Question 14

A car of mass $1400\ \mathrm{kg}$ climbs a $10^\circ$ hill at $18\ \mathrm{km/h}$. What is the power required to overcome gravity?

Accepted Answer

$P = mgv \sin 	heta$

Question 15

Which of the following statements about conservative forces is TRUE?

Accepted Answer

The work done by a conservative force is independent of the path taken

Question 16

A block attached to a horizontal spring ($k = 180\ \mathrm{N/m}$) is compressed $5.0\ \mathrm{cm}$ and released. It stretches $2.3\ \mathrm{cm}$ beyond equilibrium before stopping. What is the coefficient of kinetic friction?

Accepted Answer

$\mu_k = \dfrac{\dfrac{1}{2}k(x_1^2 - x_2^2)}{mg(x_1 + x_2)}$

Question 17

Which formula gives the period $T$ of an object in uniform circular motion in terms of frequency $f$?

Accepted Answer

$T = \dfrac{1}{f}$

Question 18

A force $F(y) = (15 	imes 10^2\ \mathrm{N/m})y - (1.9 	imes 10^3\ \mathrm{N/m^2})y^2$ acts over $y = 0$ to $y = 0.20\ \mathrm{m}$. What is the work done?

Accepted Answer

$W = \int_0^{0.20} F(y)\,dy$

PHYS 215 Test #2 Review: Forces, Newton's Laws, Circular Motion, Energy, and Power

Study Guide - Practice Questions

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