Q: A car of weight 15,000 N is being towed up a 20° slope at constant speed. If friction is negligible, what is the minimum tension required in the tow rope to keep the car moving up the hill?

$$T = 15,000 \times \sin(20^\circ)$$

Q: Which equation correctly expresses Newton's Second Law for an object in equilibrium?

$$\vec{F}_{\text{net}} = m\vec{a} = \vec{0}$$

Q: If a man stands on a scale in an elevator accelerating upward, what does the scale read?

$$W_{\text{scale}} = m(g + a)$$

Q: A 50 kg box is on a flat truck bed. If the coefficient of static friction is $$\mu_s = 0.20$$, what is the maximum acceleration the truck can have before the box starts to slide?

$$a_{\text{max}} = \mu_s g = 0.20 \times 9.8 = 1.96\ \text{m/s}^2$$

Question 1

Which of the following statements best describes mechanical equilibrium?

Accepted Answer

An object is in mechanical equilibrium if the net force acting on it is zero, resulting in no acceleration.

Question 2

A car of weight 15,000 N is being towed up a 20° slope at constant speed. If friction is negligible, what is the minimum tension required in the tow rope to keep the car moving up the hill?

Accepted Answer

$$T = 15,000 	imes \sin(20^\circ)$$

Question 3

Which equation correctly expresses Newton's Second Law for an object in equilibrium?

Accepted Answer

$$\vec{F}_{	ext{net}} = m\vec{a} = \vec{0}$$

Question 4

A box is being pulled to the right but does not move. Which statement about the static friction force $$f_s is $$correct?

Accepted Answer

$$f_s$$ increases to match the applied force up to a maximum value $$f_{s,	ext{max}}$$

Question 5

If a man stands on a scale in an elevator accelerating upward, what does the scale read?

Accepted Answer

$$W_{	ext{scale}} = m(g + a)$$

Question 6

Which of the following is true about the difference between mass and weight?

Accepted Answer

Mass is an intrinsic property of an object, while weight depends on the local gravitational field.

Question 7

A 50 kg box is on a flat truck bed. If the coefficient of static friction is $$\mu_s = 0.20$$, what is the maximum acceleration the truck can have before the box starts to slide?

Accepted Answer

$$a_{	ext{max}} = \mu_s g = 0.20 	imes 9.8 = 1.96\ 	ext{m/s}^2$$

Question 8

Which of the following best describes the direction of kinetic friction?

Accepted Answer

Kinetic friction acts opposite to the direction of motion.

Question 9

A car skids to a stop on a dry concrete road. If the coefficient of kinetic friction is $$\mu_k = 0.80$$, what is the magnitude of the friction force acting on the car?

Accepted Answer

$$f_k = \mu_k n$$

Question 10

Which of the following is NOT a correct statement about rolling friction?

Accepted Answer

Rolling friction acts perpendicular to the surface.

Question 11

If the net force on an object is constant and nonzero, which of the following is true about its motion?

Accepted Answer

The object accelerates in the direction of the net force.

Question 12

Which formula gives the 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 13

A car of mass $$m is $$pulled by a tow truck with tension $$T up a $$frictionless incline of angle $$	heta. $$What is the acceleration of the car?

Accepted Answer

$$a = \frac{T - mg \sin 	heta}{m}$$

Question 14

Which of the following is true about the reading on a scale when an object is in free fall?

Accepted Answer

The scale reads zero; the object has no apparent weight.

Question 15

Which statement about the coefficients of friction is correct?

Accepted Answer

The coefficient of static friction is usually greater than the coefficient of kinetic friction for the same materials.

Question 16

A box of mass $$m is at $$rest on a horizontal surface. If a horizontal force $$F is $$applied and the box does not move, what is the magnitude of the static friction force?

Accepted Answer

$$f_s = F$$

Question 17

Which of the following is a correct application of Newton's Second Law in the $$x-$$direction?

Accepted Answer

$$(F_{	ext{net}})_x = \sum (F_x)_i = m a_x$$

Question 18

Which of the following is true about drag force on a falling object?

Accepted Answer

Drag force increases with speed and eventually balances the gravitational force at terminal velocity.

Question 19

A car of mass $$m is $$pulled by a tow truck with tension $$T up a $$frictionless incline of angle $$	heta. $$What is the acceleration of the car?

Accepted Answer

$$a = \frac{T - mg \sin 	heta}{m}$$

Dynamics I – Motion Along a Line: Equilibrium and Newton's Second Law

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