Question 1

A 500 N orangutan hangs motionless from a vertical rope. What is the tension in the rope?

Accepted Answer

$$T = 500\ \mathrm{N}$$

Question 2

A 200 kg chandelier is supported by two cords as shown, with one cord at $$60^\circ to $$the ceiling. What is the tension in the angled cord ($$F_A$$)? (Use $$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$F_A = 2263\ \mathrm{N}$$

Question 3

A car of mass $$1500\ \mathrm{kg} is $$towed at a steady speed by a rope at $$20^\circ$$ above the horizontal. If friction is $$320\ \mathrm{N}$$, what is the tension in the rope?

Accepted Answer

$$T = 340\ \mathrm{N}$$

Question 4

A 100 kg block hangs from a rope. What is the tension if the block is accelerating upward at $$5\ \mathrm{m/s^2$}$$? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$T = 1480\ \mathrm{N}$$

Question 5

A 65 kg woman stands on a scale in an elevator accelerating downward at $$0.20g. $$What does the scale read? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$52\ \mathrm{kg}$$

Question 6

A skier of mass $$m$$ slides down a frictionless $$27^\circ$$ slope. What is the skier’s acceleration?

Accepted Answer

$$a = g\sin 27^\circ$$

Question 7

A 32 kg sofa is pushed at constant speed across a floor with $$\mu_k = 0.080. $$What force does Carol apply?

Accepted Answer

$$F = 25\ \mathrm{N}$$

Question 8

A 70 kg passenger is in a car that decelerates from $$20\ \mathrm{m/s} to $$rest in $$50\ \mathrm{m}. If$$ $$\mu_s = 0.5$$ and $$\mu_k = 0.03$$, will the passenger slide off the seat if not wearing a seat belt?

Accepted Answer

Yes, because the required friction force exceeds $$f_{s,\max}$$

Question 9

A 50 kg student stands on a scale in an elevator accelerating upward. What does the scale read?

Accepted Answer

$$\u003e 490\ \mathrm{N}$$

Question 10

A box is pulled to the right at steady speed by a rope that angles upward. How does the normal force $$n$$ compare to $$mg$$?

Accepted Answer

$$n \u003c mg$$

Question 11

A block of mass $$m$$ slides down a frictionless incline at angle $$	heta. $$What is the normal force?

Accepted Answer

$$n = mg\cos	heta$$

Question 12

A box is at rest on a rough surface. You pull with a horizontal force $$T$$, but the box does not move. What is the static friction force $$f_s$$?

Accepted Answer

$$f_s = T$$

Question 13

A 4.8 kg penguin glides in water at $$1.60\ \mathrm{m/s}$$ and decelerates at $$0.52\ \mathrm{m/s^2$}. If $$the frontal area is $$0.020\ \mathrm{m^2$}$$ and water density is $$1000\ \mathrm{kg/m^3$}$$, what is the drag coefficient $$C_D$$?

Accepted Answer

$$C_D = 0.098$$

Question 14

A pollen grain of diameter $$40\ \mu\mathrm{m}$$ falls at $$5.3\ \mathrm{cm/s} in $$air ($$\eta = 1.8 	imes 10$$^{-5}$$\ \mathrm{Pa\cdot s}). $$What is its mass in nanograms? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$37\ \mathrm{ng}$$

Question 15

Two blocks, $$m_A = 5.0\ \mathrm{kg}$$ and $$m_B = 10\ \mathrm{kg}$$, are pushed together with a $$3.0\ \mathrm{N}$$ force. What force does block A exert on block B?

Accepted Answer

$$2.0\ \mathrm{N}$$

Question 16

A 200 kg stage set is attached to a 100 kg stagehand by a rope over a frictionless pulley. When the rope is released, what is the acceleration of the stagehand? ($$g = 9.8\ \mathrm{m/s^2$})$$

Accepted Answer

$$a = 3.3\ \mathrm{m/s^2$}$$

Question 17

A box is being pulled to the right over a rough surface. The rope breaks. What happens to the box?

Accepted Answer

It slows steadily until it stops.

Question 18

A 50 kg student stands on a scale in a falling elevator (cable breaks). What does the scale read?

Accepted Answer

$$0\ \mathrm{N}$$

Ch 5 Applying Newton’s Laws: Equilibrium, Dynamics, and Friction

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