Q: A car travels 100 m east in 5 s, then 60 m west in 3 s. What is the car's average velocity for the entire trip?

$$\frac{40\ \text{m}}{8\ \text{s}} = 5\ \text{m/s}$$ east

Q: A ball is thrown straight up with an initial velocity of $$20\ \text{m/s}. $$What is its velocity after $$2\ \text{s}$$? (Assume $$g = 9.8\ \text{m/s}^2$$ downward.)

$$v = 20 - 9.8 \times 2 = 0.4\ \text{m/s}$$ upward

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

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

Q: A 5 kg mass is suspended from a spring and stretches it by 0.2 m. What is the spring constant $$k$$? (Use $$g = 9.8\ \text{m/s}^2.)$$

$$k = \frac{mg}{x} = \frac{5 \times 9.8}{0.2} = 245\ \text{N/m}$$

Q: A car accelerates from rest at $$3\ \text{m/s}^2$$ for $$4\ \text{s}. $$What is its final velocity?

$$v = v_0$ + at = 0 + 3 \times 4 = 12\ \text{m/s}$$

Q: A 10 kg box is pulled across a floor with a coefficient of kinetic friction $$\mu_k = 0.2. $$What is the frictional force?

$$F_{fk} = \mu_k F_N = 0.2 \times 10 \times 9.8 = 19.6\ \text{N}$$

Question 1

A car travels 100 m east in 5 s, then 60 m west in 3 s. What is the car's average velocity for the entire trip?

Accepted Answer

$$\frac{40\ 	ext{m}}{8\ 	ext{s}} = 5\ 	ext{m/s}$$ east

Question 2

Which of the following statements about vectors and scalars is correct?

Accepted Answer

Velocity is a vector, while speed is a scalar.

Question 3

A ball is thrown straight up with an initial velocity of $$20\ 	ext{m/s}. $$What is its velocity after $$2\ 	ext{s}$$? (Assume $$g = 9.8\ 	ext{m/s}^2$$ downward.)

Accepted Answer

$$v = 20 - 9.8 	imes 2 = 0.4\ 	ext{m/s}$$ upward

Question 4

Which graph best represents the acceleration-time graph for an object moving at constant velocity?

Accepted Answer

A horizontal line at $$a = 0 ($$see image 2).

Question 5

A projectile is launched horizontally from a cliff. Which statement is true about its motion (neglecting air resistance)?

Accepted Answer

The horizontal velocity remains constant while the vertical velocity increases due to gravity.

Question 6

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

Accepted Answer

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

Question 7

A box is at rest on a horizontal surface. The maximum static friction force is $$15\ 	ext{N}. If a$$ $$10\ 	ext{N}$$ horizontal force is applied, what happens?

Accepted Answer

The box does not move because the applied force is less than the maximum static friction.

Question 8

A 5 kg mass is suspended from a spring and stretches it by 0.2 m. What is the spring constant $$k$$? (Use $$g = 9.8\ 	ext{m/s}^2.)$$

Accepted Answer

$$k = \frac{mg}{x} = \frac{5 	imes 9.8}{0.2} = 245\ 	ext{N/m}$$

Question 9

A car accelerates from rest at $$3\ 	ext{m/s}^2$$ for $$4\ 	ext{s}. $$What is its final velocity?

Accepted Answer

$$v = v_0$ + at = 0 + 3 	imes 4 = 12\ 	ext{m/s}$$

Question 10

A 10 kg box is pulled across a floor with a coefficient of kinetic friction $$\mu_k = 0.2. $$What is the frictional force?

Accepted Answer

$$F_{fk} = \mu_k F_N = 0.2 	imes 10 	imes 9.8 = 19.6\ 	ext{N}$$

Question 11

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 force.

Question 12

A projectile is launched at an angle $$	heta$$ with initial speed $$v_i. $$What is the formula for its maximum height?

Accepted Answer

$$h_{max} = \frac{v_{iy}^2}{2g}$$

Question 13

A 70 kg person stands on a scale in an elevator accelerating upward at $$2\ 	ext{m/s}^2. $$What is the apparent weight?

Accepted Answer

$$F_{apparent} = m(g + a) = 70 	imes (9.8 + 2) = 826\ 	ext{N}$$

Question 14

Which of the following is NOT a fundamental force?

Accepted Answer

Frictional force

Question 15

A boat moves east at $$5\ 	ext{m/s}$$ relative to the water, and the water flows north at $$3\ 	ext{m/s}$$ relative to the ground. What is the boat's speed relative to the ground?

Accepted Answer

$$v = \sqrt{5^2$ + 3^2$} = \sqrt{34} \approx 5.83\ 	ext{m/s}$$

Question 16

Which of the following statements about inertia is correct?

Accepted Answer

Inertia is the tendency of an object to resist changes in its state of motion.

Question 17

A 1 kg object is dropped from rest from a height of 20 m. How long does it take to reach the ground? (Neglect air resistance, $$g = 9.8\ 	ext{m/s}^2)$$

Accepted Answer

$$t = \sqrt{\frac{2h}{g}} = \sqrt{\frac{2 	imes 20}{9.8}} \approx 2.02\ 	ext{s}$$

Question 18

Which of the following best describes the tip-to-tail method for vector addition?

Accepted Answer

Placing the tail of one vector at the head of another and drawing the resultant from the tail of the first to the head of the last.

Physics Study Guide: Kinematics, Vectors, and Newton's Laws

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