Q: A 0.55 kg ball attached to the end of a horizontal cord is revolved in a circle of radius 1.3 m on a frictionless horizontal surface. If the cord will break when a force exceeds 75 N, what is the maximum speed the ball can move at?

$$v = \sqrt{\frac{75 \times 1.3}{0.55}}$$

Q: Two blocks, with masses 600 kg and 400 kg, are connected by a cable and pulled by a force of 2000 N as shown. If the coefficient of kinetic friction is 0.2, what is the acceleration of the blocks?

$$a = \frac{2000 - (1000 \times 0.2 \times 9.8)}{1000}$$

Q: During a workout, football players run up the stadium stairs. If the stairs are 10 m high and the average mass of a player is 80 kg, what is the work done against gravity for one player?

$$W = mgh = 80 \times 9.8 \times 10$$

Q: A 18 kg sled starts up a 26 degree slope with a speed of 2.3 m/s. The coefficient of kinetic friction between the sled and slope is 0.25. How far up the slope does the sled travel before stopping?

$$d = \frac{v^2$}{2g(\sin\theta + \mu_k \cos\theta)}$$

Q: A 51 kg skier starts down a 20 degree slope. What is the acceleration of the skier if the coefficient of kinetic friction is 0.12?

$$a = g (\sin\theta - \mu_k \cos\theta)$$

Question 1

A 60.5 kg student standing on a scale in an elevator notices that the scale reads 573 N. If the elevator is accelerating upward, what is the acceleration of the elevator?

Accepted Answer

$$a = \frac{573}{60.5} - 9.8$$

Question 2

A 0.55 kg ball attached to the end of a horizontal cord is revolved in a circle of radius 1.3 m on a frictionless horizontal surface. If the cord will break when a force exceeds 75 N, what is the maximum speed the ball can move at?

Accepted Answer

$$v = \sqrt{\frac{75 	imes 1.3}{0.55}}$$

Question 3

Two blocks, with masses 600 kg and 400 kg, are connected by a cable and pulled by a force of 2000 N as shown. If the coefficient of kinetic friction is 0.2, what is the acceleration of the blocks?

Accepted Answer

$$a = \frac{2000 - (1000 	imes 0.2 	imes 9.8)}{1000}$$

Question 4

A child whirls a ball in a vertical circle. At which point is the tension in the cord greatest?

Accepted Answer

At the bottom of the circle

Question 5

A car maintains a constant speed as it travels over a hill and valley. At which point is the normal force acting on the car the greatest?

Accepted Answer

At the bottom of the valley

Question 6

A 725 kg space rocket is traveling at a speed of $$6.0 	imes 10^3$ m/s away from the Earth when it ejects 1.0 kg of gas at a speed of 2.4$$ 	imes $$10^4 m/s $$relative to the rocket. What is the change in speed of the rocket?

Accepted Answer

$$\Delta v = \frac{m_{gas} v_{gas}}{m_{rocket}}$$

Question 7

Suppose you lift a suitcase from the floor to a table. The work you do on the suitcase depends on which of the following?

Accepted Answer

The height of the table above the floor

Question 8

During a workout, football players run up the stadium stairs. If the stairs are 10 m high and the average mass of a player is 80 kg, what is the work done against gravity for one player?

Accepted Answer

$$W = mgh = 80 	imes 9.8 	imes 10$$

Question 9

A spring does not follow Hooke's law but instead requires a force $$F(x) = ax^2$ to deform. What is the work required to stretch the spring from x = 0$ to x$$ = $$x_0$$?

Accepted Answer

$$W = \frac{a}{3} x_0$^3$$

Question 10

A box slides on a horizontal, frictionless surface. A nonconstant force $$F is $$applied to it as shown in the graph. How much work is done as the box moves from $$x = 0 to$$ $$x = 10 m$$?

Accepted Answer

The area under the force vs. displacement graph

Question 11

A 18 kg sled starts up a 26 degree slope with a speed of 2.3 m/s. The coefficient of kinetic friction between the sled and slope is 0.25. How far up the slope does the sled travel before stopping?

Accepted Answer

$$d = \frac{v^2$}{2g(\sin	heta + \mu_k \cos	heta)}$$

Question 12

A car generates 15 kW horsepower at a steady 95 km/h. What is the average force exerted on the car due to friction and air resistance?

Accepted Answer

$$F = \frac{P}{v}$$

Question 13

An atomic nucleus at rest decays radioactively into an alpha particle and a different nucleus. If the speed of the alpha particle is $$2.8 	imes 10^7$ m/s and the mass of the nucleus is 57 times greater than that of the alpha particle, what is the speed of the resulting nucleus?

Accepted Answer

$$v_{nucleus} = \frac{m_{alpha} v_{alpha}}{m_{nucleus}}$$

Question 14

Suppose you fire a ball of mass 0.12 kg vertically into the air by compressing a spring 15 cm from its natural length (k = 52 N/m). What is the spring constant k if the ball reaches a maximum height of 6.3 m?

Accepted Answer

$$k = \frac{2 m g h}{x^2$}$$

Question 15

A 51 kg skier starts down a 20 degree slope. What is the acceleration of the skier if the coefficient of kinetic friction is 0.12?

Accepted Answer

$$a = g (\sin	heta - \mu_k \cos	heta)$$

Question 16

A rocket with a mass of 1800 kg at rest fires its engine and ejects gas at a speed of $$4.3 	imes 10^3$ m/s. What is the change in speed of the rocket if 1.0 kg of gas is ejected?

Accepted Answer

$$\Delta v = \frac{m_{gas} v_{gas}}{m_{rocket}}$$

Physics 2A-32211 Exam #2 Review Exercises – Step-by-Step Study Guidance

Guida di studio - Domande di pratica

Study guide - Flashcard