Q: Eratosthenes measured the size of the Earth by observing the angle of the Sun's rays at two different locations. If the distance between the two cities is 800 km and the angle difference is $$7.2^{\circ}$$, what is the approximate circumference of the Earth according to his method?

$$800 \text{ km} \times \frac{360$$^{\circ}$$}{7.2$$^{\circ}$$} = 40,000 \text{ km}$$

Q: A runner accelerates from rest to $$10 \text{ m/s} in$$ $$10 \text{ s}. $$What is the runner's acceleration?

$$a = \frac{\Delta v}{\Delta t} = \frac{10 \text{ m/s} - 0}{10 \text{ s}} = 1 \text{ m/s}^2$$

Q: A $$2 \text{ kg}$$ object is acted on by a $$10 \text{ N}$$ force. What is its acceleration?

$$a = \frac{F}{m} = \frac{10 \text{ N}}{2 \text{ kg}} = 5 \text{ m/s}^2$$

Question 1

Eratosthenes measured the size of the Earth by observing the angle of the Sun's rays at two different locations. If the distance between the two cities is 800 km and the angle difference is $$7.2^{\circ}$$, what is the approximate circumference of the Earth according to his method?

Accepted Answer

$$800 	ext{ km} 	imes \frac{360$$^{\circ}$$}{7.2$$^{\circ}$$} = 40,000 	ext{ km}$$

Question 2

Which of the following best describes a scientific hypothesis?

Accepted Answer

A tentative explanation that can be tested by experiment or observation

Question 3

Which of the following is NOT a step in the scientific method?

Accepted Answer

Ignoring contradictory evidence

Question 4

A runner accelerates from rest to $$10 	ext{ m/s} in$$ $$10 	ext{ s}. $$What is the runner's acceleration?

Accepted Answer

$$a = \frac{\Delta v}{\Delta t} = \frac{10 	ext{ m/s} - 0}{10 	ext{ s}} = 1 	ext{ m/s}^2$$

Question 5

Which statement about mechanical equilibrium is correct?

Accepted Answer

The net force acting on the object is zero

Question 6

If the net force acting on an object is zero, which of the following is true?

Accepted Answer

The object is either at rest or moving with constant velocity

Question 7

Galileo's Leaning Tower of Pisa experiment demonstrated that:

Accepted Answer

Objects of different masses fall at the same rate in the absence of air resistance

Question 8

Which of the following is the correct formula for Newton's Second Law of Motion?

Accepted Answer

$$F = ma$$

Question 9

A $$2 	ext{ kg}$$ object is acted on by a $$10 	ext{ N}$$ force. What is its acceleration?

Accepted Answer

$$a = \frac{F}{m} = \frac{10 	ext{ N}}{2 	ext{ kg}} = 5 	ext{ m/s}^2$$

Question 10

Which of the following best describes the difference between mass and weight?

Accepted Answer

Mass is the amount of matter in an object; weight is the force of gravity acting on that mass

Question 11

What is the equation for gravitational force between two masses $$m_1$$ and $$m_2$$ separated by distance $$r$$?

Accepted Answer

$$F = G \frac{m_1$ m_2$}{r^2$}$$

Question 12

If the distance between two objects is doubled, what happens to the gravitational force between them?

Accepted Answer

It becomes one-fourth as strong

Question 13

Which of the following is the correct formula for kinetic energy?

Accepted Answer

$$KE = \frac{1}{2}mv^2$

Question 14

A $$5 	ext{ kg}$$ object is lifted to a height of $$10 	ext{ m}. $$What is its potential energy? (Assume $$g = 9.8 	ext{ m/s}^2)$$

Accepted Answer

$$PE = mgh = 5 	ext{ kg} 	imes 9.8 	ext{ m/s}^2 	imes 10 	ext{ m} = 490 	ext{ J}$$

Question 15

If the speed of an object is doubled, by what factor does its kinetic energy increase?

Accepted Answer

By a factor of 4

Question 16

Which of the following best explains why machines cannot be 100% efficient?

Accepted Answer

Some energy is always lost to friction and heat

Question 17

Which of the following is a correct statement about the conservation of energy?

Accepted Answer

Energy cannot be created or destroyed, only transformed from one form to another

Question 18

A $$60 	ext{ kg}$$ person stands on a scale in an elevator accelerating upward at $$2 	ext{ m/s}^2. $$What does the scale read? (Assume $$g = 9.8 	ext{ m/s}^2)$$

Accepted Answer

$$F = m(g + a) = 60 	ext{ kg} 	imes (9.8 + 2) 	ext{ m/s}^2 = 708 	ext{ N}$$

Question 19

Which of the following best describes terminal velocity?

Accepted Answer

The constant speed reached when the force of air resistance equals the force of gravity

Physics Midterm Exam Study Guide: Classical Mechanics and Gravitation

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