Q: A person of weight $$W$$ stands on an oak board inclined at angle $$\theta. If $$the static coefficient of friction is $$\mu_s = 0.6$$, what is the maximum angle $$\theta$$ before the person begins to slide?

$$\theta = \arctan(0.6) \approx 31^\circ$$

Q: A 70 kg person jumps up to a height of 0.6 m once every second for 10 minutes. If muscle efficiency is 20%, what is the total energy required from food to perform this activity?

$$E = \frac{70 \times 9.8 \times 0.6 \times 600}{0.2} \approx 123,000 \text{ J}$$

Q: A steel block slides on ice. If the static coefficient of friction is $$\mu_s = 0.02$$ and the normal force is $$100 N$$, what is the maximum static friction force?

$$F_{f,\text{max}} = 0.02 \times 100 = 2 \text{ N}$$

Q: A person stands on an incline. Which condition must be met to prevent sliding?

$$W \sin \theta \leq \mu_s W \cos \theta$$

Question 1

Which equation correctly expresses the frictional force $$F_f$$ acting on an object pressed against a surface with normal force $$F_n$$ and coefficient of friction $$\mu$$?

Accepted Answer

$$F_f = \mu F_n$$

Question 2

A person of weight $$W$$ stands on an oak board inclined at angle $$	heta. If $$the static coefficient of friction is $$\mu_s = 0.6$$, what is the maximum angle $$	heta$$ before the person begins to slide?

Accepted Answer

$$	heta = \arctan(0.6) \approx 31^\circ$$

Question 3

Which of the following surfaces has the lowest kinetic coefficient of friction according to the provided data?

Accepted Answer

Bone on joint, lubricated

Question 4

When a person walks, why is the force on the hip joint greater than the person's weight?

Accepted Answer

Because the center of gravity is not directly above the joint, resulting in a larger force due to leverage.

Question 5

A 70 kg person jumps up to a height of 0.6 m once every second for 10 minutes. If muscle efficiency is 20%, what is the total energy required from food to perform this activity?

Accepted Answer

$$E = \frac{70 	imes 9.8 	imes 0.6 	imes 600}{0.2} \approx 123,000 	ext{ J}$$

Question 6

Which factor most effectively reduces frictional wear at the hip joint during walking?

Accepted Answer

Presence of smooth cartilage and synovial fluid

Question 7

For an object moving with uniform acceleration $$a$$, which equation gives the distance $$s$$ traversed after time $$t$$ starting from initial velocity $$v_0$$?

Accepted Answer

$$s = v_0$ t + \frac{a t^2$}{2}$$

Question 8

A steel block slides on ice. If the static coefficient of friction is $$\mu_s = 0.02$$ and the normal force is $$100 N$$, what is the maximum static friction force?

Accepted Answer

$$F_{f,	ext{max}} = 0.02 	imes 100 = 2 	ext{ N}$$

Question 9

Which equation correctly relates the final velocity $$v to $$the initial velocity $$v_0$$, acceleration $$a$$, and distance $$s$$ for an object under uniform acceleration?

Accepted Answer

$$v^2$$ = $$v_0^2 + 2 a s$

Question 10

A person stands on an incline. Which condition must be met to prevent sliding?

Accepted Answer

$$W \sin 	heta \leq \mu_s W \cos 	heta$$

Question 11

During walking, the force on the hip joint can be up to how many times the body weight?

Accepted Answer

About 5 times the body weight

Question 12

Which of the following best describes kinetic friction?

Accepted Answer

The frictional force acting on a moving object, proportional to $$\mu_k$$

Question 13

If a person of weight $$W$$ stands on a surface with coefficient of static friction $$\mu_s$$, what is the maximum horizontal force that can be applied before the person starts sliding?

Accepted Answer

$$F_{	ext{max}} = \mu_s W$$

Question 14

Which of the following statements about muscle efficiency in converting food energy to work is correct?

Accepted Answer

Muscle efficiency is less than 20%

Question 15

A person jumps vertically with a take-off velocity $$v_0. $$What is the maximum height $$H$$ reached, neglecting air resistance?

Accepted Answer

$$H = \frac{v_0$^2}{2g}$$

Question 16

Which of the following is NOT a method by which the body reduces frictional wear at the joints?

Accepted Answer

Increasing the roughness of cartilage

Question 17

If the net upward force on a jumper is $$F - W$$ and the acceleration occurs over a distance $$c$$, what is the take-off velocity $$v$$?

Accepted Answer

$$v = \sqrt{2(F - W)c / m}$$

Question 18

Which equation gives the average velocity $$v_{av}$$ during a time interval $$t$$ for an object accelerating uniformly from $$v_0 to$$ $$v$$?

Accepted Answer

$$v_{av} = \frac{v + v_0$}{2}$$

Biophysics: Friction, Translational Motion, and Energy in Physical Activity

스터디 가이드 - 연습 문제

학습 가이드 - 플래시카드