Q: Which of the following equations best represents Newton's First Law of Motion?

$$\vec{F}_{\text{net}} = 0 \iff \frac{d\vec{v}}{dt} = 0$$

Q: A constant upward force of $$74.0\ \text{N} is $$applied to box A, which is connected by a rope to box B. If box B descends $$13.0\ \text{m} in$$ $$4.50\ \text{s}$$, what is the acceleration of box B?

$$a = \frac{2 \times 13.0}{(4.50)^2$}$$

Q: A $$4.00\ \text{kg}$$ and a $$6.00\ \text{kg}$$ crate are connected by a rope and pulled with a force $$F. If $$the acceleration of the system is $$a$$, what is the tension $$T in $$the rope between the crates?

$$T = 4.00\ \text{kg} \times a$$

Question 1

Which of the following equations best represents Newton's First Law of Motion?

Accepted Answer

$$\vec{F}_{	ext{net}} = 0 \iff \frac{d\vec{v}}{dt} = 0$$

Question 2

A shell is fired from the edge of a cliff with an initial velocity of $$15.0\ 	ext{m/s} at$$ $$35.0^\circ$$ above the horizontal. What is the horizontal velocity of the shell at $$t = 2.50\ 	ext{s}$$? (Neglect air resistance.)

Accepted Answer

$$12.3\ 	ext{m/s}$$

Question 3

Which of the following statements about Newton's Third Law is correct?

Accepted Answer

The forces two objects exert on each other are equal in magnitude and opposite in direction.

Question 4

A woman pulls on a $$6.00\ 	ext{kg}$$ crate, which is connected to a $$4.00\ 	ext{kg}$$ crate by a light rope. Compared to the $$6.00\ 	ext{kg}$$ crate, the lighter $$4.00\ 	ext{kg}$$ crate:

Accepted Answer

is subjected to a smaller net force and has the same acceleration.

Question 5

Which equation should be used to find the mass of box B if it descends $$13.0\ 	ext{m} in$$ $$4.50\ 	ext{s}$$, given the tension in the rope is $$38.0\ 	ext{N}$$?

Accepted Answer

$$T - m_B g = -m_B a_{B,y}$$

Question 6

A box is in equilibrium on a frictionless surface. Which of the following must be true?

Accepted Answer

$$\sum \vec{F} = 0$$

Question 7

You are standing at rest and begin to walk forward. What force actually pushes you forward?

Accepted Answer

The force of the ground on your feet

Question 8

If the net force on an object is not zero, which of the following is true according to Newton's Second Law?

Accepted Answer

The object has acceleration in the same direction as the net force.

Question 9

A constant upward force of $$74.0\ 	ext{N} is $$applied to box A, which is connected by a rope to box B. If box B descends $$13.0\ 	ext{m} in$$ $$4.50\ 	ext{s}$$, what is the acceleration of box B?

Accepted Answer

$$a = \frac{2 	imes 13.0}{(4.50)^2$}$$

Question 10

Which of the following is the correct free-body diagram for box B in the two-box system described?

Accepted Answer

Upward tension, downward weight

Question 11

A $$10\ 	ext{kg}$$ box is pulled across a frictionless surface with a net force of $$20\ 	ext{N}. $$What is its acceleration?

Accepted Answer

$$a = 2\ 	ext{m/s}^2$$

Question 12

If the sum of the x-components of force on an object is zero, what can be concluded about the object's motion in the x-direction?

Accepted Answer

The object's velocity in the x-direction is constant.

Question 13

A $$5.0\ 	ext{kg}$$ object is acted on by two forces: $$\vec{F}_1 = 10\ 	ext{N}$$ east and $$\vec{F}_2 = 10\ 	ext{N}$$ west. What is the acceleration of the object?

Accepted Answer

$$a = 0\ 	ext{m/s}^2$$

Question 14

Which of the following best describes the relationship between the net force and acceleration of an object?

Accepted Answer

The net force is always in the same direction as the acceleration.

Question 15

A $$4.00\ 	ext{kg}$$ and a $$6.00\ 	ext{kg}$$ crate are connected by a rope and pulled with a force $$F. If $$the acceleration of the system is $$a$$, what is the tension $$T in $$the rope between the crates?

Accepted Answer

$$T = 4.00\ 	ext{kg} 	imes a$$

Question 16

If $$\vec{F}_{12} = -\vec{F}_{21}$$, what does this equation represent?

Accepted Answer

Newton's Third Law

Question 17

A box is pulled upward with a force $$F$$ while its weight is $$mg$$ and the tension in the rope is $$T. $$Which equation correctly represents the net force on the box?

Accepted Answer

$$F - T - mg = -ma$$

Question 18

A $$2.0\ 	ext{kg}$$ object is in free fall. What is the net force acting on it?

Accepted Answer

$$F_{	ext{net}} = 19.6\ 	ext{N}$$

Question 19

Which of the following is a correct statement about equilibrium?

Accepted Answer

An object in equilibrium has zero net force acting on it.

Newton’s Laws of Motion and Applications: Study Notes for University Physics I

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