Q: A ball is thrown vertically upward with an initial velocity of $$v_0 = 15$$\ \mathrm{m/s}$$. Neglecting air resistance, what is the maximum height reached by the ball?

$$h = \frac{v_0$^2}{2g} = \frac{(15)^2$}{2 \times 9.8} \approx 11.5\ \mathrm{m}$$

Q: A 5 kg box is pulled across a horizontal surface with a constant force of 20 N. If the coefficient of kinetic friction is $$\mu_k = 0.2$$, what is the acceleration of the box?

$$a = \frac{F - f_k}{m} = \frac{20 - (0.2 \times 5 \times 9.8)}{5} = \frac{20 - 9.8}{5} = 2.04\ \mathrm{m/s^2$}$$

Q: A projectile is launched at an angle $$\theta = 30^\circ$$ with an initial speed of $$v_0 = 40$$\ \mathrm{m/s}$$. What is the horizontal range of the projectile? (Assume g = 9.8$$\ \mathrm{$$m/s^2$$}$$ and neglect air resistance.)

$$R = \frac{v_0$^2 \sin(2\theta)}{g} = \frac{(40)^2$ \sin(60^\circ)}{9.8} \approx 141\ \mathrm{m}$$

Q: A 10 kg object is suspended from a spring scale in an elevator accelerating upward at $$2\ \mathrm{m/s^2$}. $$What is the reading on the scale?

$$F = m(g + a) = 10 \times (9.8 + 2) = 118\ \mathrm{N}$$

Question 1

A car accelerates uniformly from rest to a speed of 20 m/s in 10 seconds. What is the car's acceleration?

Accepted Answer

$$a = \frac{20\ \mathrm{m/s}}{10\ \mathrm{s}} = 2\ \mathrm{m/s^2$}$$

Question 2

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

Accepted Answer

An object at rest remains at rest, and an object in motion remains in motion at constant velocity unless acted upon by a net external force.

Question 3

A ball is thrown vertically upward with an initial velocity of $$v_0 = 15$$\ \mathrm{m/s}$$. Neglecting air resistance, what is the maximum height reached by the ball?

Accepted Answer

$$h = \frac{v_0$^2}{2g} = \frac{(15)^2$}{2 	imes 9.8} \approx 11.5\ \mathrm{m}$$

Question 4

A 5 kg box is pulled across a horizontal surface with a constant force of 20 N. If the coefficient of kinetic friction is $$\mu_k = 0.2$$, what is the acceleration of the box?

Accepted Answer

$$a = \frac{F - f_k}{m} = \frac{20 - (0.2 	imes 5 	imes 9.8)}{5} = \frac{20 - 9.8}{5} = 2.04\ \mathrm{m/s^2$}$$

Question 5

Which of the following is a correct unit for work in the SI system?

Accepted Answer

Joule ($$J)$$

Question 6

A projectile is launched at an angle $$	heta = 30^\circ$$ with an initial speed of $$v_0 = 40$$\ \mathrm{m/s}$$. What is the horizontal range of the projectile? (Assume g = 9.8$$\ \mathrm{$$m/s^2$$}$$ and neglect air resistance.)

Accepted Answer

$$R = \frac{v_0$^2 \sin(2	heta)}{g} = \frac{(40)^2$ \sin(60^\circ)}{9.8} \approx 141\ \mathrm{m}$$

Question 7

Which statement best explains why astronauts feel 'weightless' while orbiting Earth?

Accepted Answer

They are in free fall, accelerating toward Earth at the same rate as their spacecraft.

Question 8

A block of mass $$m$$ slides down a frictionless incline of height $$h. $$What is its speed at the bottom?

Accepted Answer

$$v = \sqrt{2gh}$$

Question 9

A 2 kg object moving at 3 m/s collides elastically with a stationary 1 kg object. What is the velocity of the 2 kg object after the collision?

Accepted Answer

$$v_1$$' = \frac{$$m_1$$ - $$m_2$$}{$$m_1$$ + $$m_2$$} $$v_1$$ = \frac{2 - 1}{2 + 1} 	imes 3 = 1\ \mathrm{m/s}$$

Question 10

Which of the following quantities is NOT a vector?

Accepted Answer

Speed

Question 11

A 10 kg object is suspended from a spring scale in an elevator accelerating upward at $$2\ \mathrm{m/s^2$}. $$What is the reading on the scale?

Accepted Answer

$$F = m(g + a) = 10 	imes (9.8 + 2) = 118\ \mathrm{N}$$

Question 12

Which of the following best describes the work done by gravity when lifting a box vertically upward?

Accepted Answer

Gravity does negative work equal to $$-mgh.$$

Question 13

A cyclist increases her speed from 5 m/s to 15 m/s. By what factor does her kinetic energy increase?

Accepted Answer

Factor of 9

Question 14

A ball is dropped from a height of 20 m. How long does it take to reach the ground? (Assume $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$t = \sqrt{\frac{2h}{g}} = \sqrt{\frac{40}{9.8}} \approx 2.02\ \mathrm{s}$$

Question 15

Which of the following is the correct expression for the centripetal force acting on a mass $$m$$ moving in a circle of radius $$r at $$speed $$v$$?

Accepted Answer

$$F_c = \frac{mv^2$}{r}$$

Question 16

A 0.5 kg mass attached to a spring oscillates with a period of 2 seconds. What is the spring constant $$k$$?

Accepted Answer

$$T = 2\pi \sqrt{\frac{m}{k}} \Rightarrow k = \frac{4\pi^2$ m}{T^2$} = \frac{4 	imes \pi^2$ 	imes 0.5}{4} \approx 4.93\ \mathrm{N/m}$$

Question 17

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

Accepted Answer

The total energy of the system remains constant; energy can change forms but is neither created nor destroyed.

Question 18

A 3 kg object moving at 4 m/s collides inelastically with a 2 kg object at rest. What is their final velocity after the collision?

Accepted Answer

$$v_f = \frac{m_1$ v_1$ + m_2$ v_2$}{m_1$ + m_2$} = \frac{3 	imes 4 + 2 	imes 0}{3 + 2} = \frac{12}{5} = 2.4\ \mathrm{m/s}$$

PHYS121-01/02: University Physics I & PHYS210-01/02: Introductory Physics Laboratory (Syllabus and Course Structure)

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