Q: A penguin slides down an icy incline of $$10.0^\circ$$ with a mass of $$32.0 kg. If $$the coefficient of kinetic friction is $$0.05$$, what is the force of kinetic friction?

$$f_k = \mu_k N = 0.05 \times 32.0 \times 9.8 \approx 15.7 N$$

Question 1

A ball is launched from ground level with an initial speed $$v_0 at an $$angle $$\$$theta_0$$ above the horizontal. Which equation correctly gives the time of flight until the ball returns to ground level?

Accepted Answer

$$t = \frac{2 v_0$ \sin \$$theta_0$$}{g}$$

Question 2

A hockey puck slides across ice with a constant velocity. Which statement best explains why the puck eventually slows down and stops?

Accepted Answer

Kinetic friction between the puck and ice opposes its motion.

Question 3

A car moves from point $$P_1 at$$ $$(3.0, 1.0) m to $$point $$P_2 at$$ $$(4.0, 5.0) m in$$ $$0.5 s. $$What is the magnitude of its average velocity?

Accepted Answer

$$\sqrt{(4.0-3.0)^2$ + (5.0-1.0)^2$}/0.5 = \sqrt{1^2$ + 4^2$}/0.5 = \sqrt{17}/0.5 \approx 8.25 m/s$$

Question 4

Which of the following best describes the direction of the frictional force acting on a moving object?

Accepted Answer

It acts opposite to the direction of motion.

Question 5

A block is held against a wall by a horizontal force. What determines the maximum vertical force that can be applied before the block slides down?

Accepted Answer

The maximum static friction, which depends on the normal force and the coefficient of static friction.

Question 6

Which equation gives the range $$R of a $$projectile launched from ground level with initial speed $$v_0 at $$angle $$\$$theta_0$$?

Accepted Answer

$$R = \frac{v_0$^2 \sin 2\$$theta_0$$}{g}$$

Question 7

A child pulls a toy chest with a rope. The chest starts moving when the applied force exceeds which quantity?

Accepted Answer

The maximum static friction force.

Question 8

Which statement about Newton's laws is correct?

Accepted Answer

They are universal and apply to all objects and situations.

Question 9

A penguin slides down an icy incline of $$10.0^\circ$$ with a mass of $$32.0 kg. If $$the coefficient of kinetic friction is $$0.05$$, what is the force of kinetic friction?

Accepted Answer

$$f_k = \mu_k N = 0.05 	imes 32.0 	imes 9.8 \approx 15.7 N$$

Question 10

Which of the following is NOT a factor that significantly affects friction for most solid objects?

Accepted Answer

Surface area of contact

Question 11

A projectile is launched with initial velocity components $$v_{0x}$$ and $$v_{0y}. $$Which equation gives its vertical position $$y(t) at $$time $$t$$?

Accepted Answer

$$y(t) = y_0$ + v_{0y} t - \frac{1}{2} g t^2$

Question 12

Which of the following best describes the normal force acting on an object resting on a horizontal surface?

Accepted Answer

It acts perpendicular to the surface and supports the object's weight.

Question 13

A free-body diagram is useful for which of the following purposes?

Accepted Answer

Visualizing the forces acting on an object and predicting its motion.

Question 14

Which equation correctly gives the magnitude of the position vector $$\vec{r}$$ for a point $$(x, y) in $$the plane?

Accepted Answer

$$|\vec{r}| = \sqrt{x^2$ + y^2$}$$

Question 15

Which of the following statements about static friction is true?

Accepted Answer

Static friction adjusts up to its maximum value to prevent motion.

Question 16

A projectile is launched at an angle $$\$$theta_0$$ with initial speed v_0$. What is the initial vertical velocity component?

Accepted Answer

$$v_{0y} = v_0$ \sin \$$theta_0$$

Question 17

Which of the following is a correct statement about the acceleration vector in projectile motion?

Accepted Answer

It always points downward with magnitude $$g.$$

Question 18

A block of mass $$m is $$pulled across a horizontal surface with a constant force $$F. If $$the coefficient of kinetic friction is $$\mu_k$$, what is the acceleration of the block?

Accepted Answer

$$a = \frac{F - \mu_k m g}{m}$$

Question 19

Which of the following is NOT a universal law according to Newton's Principia?

Accepted Answer

The law of conservation of energy

Study Notes: Two-Dimensional Motion, Friction, and Newton's Laws

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