Q: A 3 kg object is acted upon by two forces: $$\vec{F}_1 = 4 \\ \mathrm{N}$$ east and $$\vec{F}_2 = 3 \\ \mathrm{N}$$ north. What is the magnitude of the object's acceleration?

$$a = 1.67 \\ \mathrm{m/s^2$}$$

Q: Two blocks, $$m_1 = 2$$ \\ \mathrm{kg}$$ and m_2$ = 3 \\ \mathrm{kg}$$, are connected by a light string over a frictionless pulley. $$m_1$$ hangs vertically, $$m_2$$ rests on a frictionless table. What is the acceleration of the system?

$$a = 1.96 \\ \mathrm{m/s^2$}$$

Q: A person pushes a box 3 m across a floor with a force of 20 N at an angle of $$60^\circ$$ above the horizontal. How much work is done by the person?

$$W = 20 \times 3 \times \cos 60^\circ = 30 \\ \mathrm{J}$$

Question 1

A 2 kg block is pulled to the right with a constant force of 10 N on a frictionless surface. What is the acceleration of the block?

Accepted Answer

$$a = 5 \ \mathrm{m/s^2$}$$

Question 2

A 3 kg object is acted upon by two forces: $$\vec{F}_1 = 4 \ \mathrm{N}$$ east and $$\vec{F}_2 = 3 \ \mathrm{N}$$ north. What is the magnitude of the object's acceleration?

Accepted Answer

$$a = 1.67 \ \mathrm{m/s^2$}$$

Question 3

Which of the following best describes the difference between speed and velocity?

Accepted Answer

Speed is the magnitude of velocity; velocity includes direction.

Question 4

The acceleration due to gravity $$g at $$the surface of a planet of mass $$M$$ and radius $$R is $$given by which formula?

Accepted Answer

$$g = \dfrac{GM}{R^2$}$$

Question 5

Which of the following is the correct definition of weight?

Accepted Answer

Weight is the force of gravity acting on an object: $$W = mg.$$

Question 6

A 5 kg box rests on a horizontal surface. The coefficient of static friction is 0.4. What is the maximum force that can be applied horizontally before the box starts to move?

Accepted Answer

$$F_{max} = 20 \ \mathrm{N}$$

Question 7

Two blocks, $$m_1 = 2$$ \ \mathrm{kg}$$ and m_2$ = 3 \ \mathrm{kg}$$, are connected by a light string over a frictionless pulley. $$m_1$$ hangs vertically, $$m_2$$ rests on a frictionless table. What is the acceleration of the system?

Accepted Answer

$$a = 1.96 \ \mathrm{m/s^2$}$$

Question 8

A car of mass $$m$$ travels at speed $$v$$ around a banked curve of radius $$r$$ with banking angle $$	heta. If $$there is no friction, what is the correct expression for the speed at which the car can travel without sliding?

Accepted Answer

$$v = \sqrt{rg 	an 	heta}$$

Question 9

A skydiver of mass $$m$$ falls through the air and eventually reaches terminal speed. Which of the following statements is true at terminal speed?

Accepted Answer

The force of gravity equals the resistive force of air.

Question 10

The resistive force on a falling object is given by $$F_{resist} = bv$$, where $$b is a $$constant. What is the expression for the terminal speed $$v_t$$?

Accepted Answer

$$v_t = \dfrac{mg}{b}$$

Question 11

A force $$\vec{F}$$ acts on an object, causing a displacement $$\vec{d}. $$The work done by the force is given by which expression?

Accepted Answer

$$W = Fd \cos 	heta$$

Question 12

A person pushes a box 3 m across a floor with a force of 20 N at an angle of $$60^\circ$$ above the horizontal. How much work is done by the person?

Accepted Answer

$$W = 20 	imes 3 	imes \cos 60^\circ = 30 \ \mathrm{J}$$

Question 13

Which of the following statements about the sign of work is correct?

Accepted Answer

Work is negative if the force and displacement are in opposite directions.

Question 14

A 0.5 kg ball is dropped from a height of 10 m. Ignoring air resistance, what is its speed just before hitting the ground? (Use $$g = 9.8 \ \mathrm{m/s^2$})$$

Accepted Answer

$$v = 14 \ \mathrm{m/s}$$

Question 15

A block of mass $$m is $$attached to a horizontal spring with spring constant $$k. $$The block is pulled a distance $$x$$ and released from rest. If there is friction with coefficient $$\mu_k$$, what is the speed of the block as it passes through equilibrium?

Accepted Answer

$$v = \sqrt{\dfrac{kx^2$}{m} - 2\mu_k g x}$$

Question 16

Which of the following best describes the principle of conservation of energy?

Accepted Answer

The total energy of an isolated system remains constant.

Question 17

A 2 kg object is launched by a horizontal spring (spring constant $$k = 200 \ \mathrm{N/m}) $$compressed by 0.1 m. If the object slides on a surface with friction ($$\mu_k = 0.1) $$for 2 m, what is its speed after leaving the spring?

Accepted Answer

$$v = 0.7 \ \mathrm{m/s}$$

Question 18

Which of the following is the correct definition of density?

Accepted Answer

Density is the ratio of mass to volume: $$\rho = \dfrac{m}{V}.$$

Exam 2 Study Guide: Forces, Gravitation, Circular Motion, Work, and Energy

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