Q: A Boeing 737 (mass $$51,000\ \mathrm{kg}) $$accelerates down a runway from rest to takeoff speed over $$940\ \mathrm{m}$$, reaching an acceleration of $$2.61\ \mathrm{m/s^2$}. $$What is the total thrust produced by both engines?

$$F = m a = 51,000 \times 2.61 = 133,110\ \mathrm{N}$$

Question 1

A car of mass 1200 kg is acted upon by a net force of 3600 N. What is the acceleration of the car?

Accepted Answer

$$a = \frac{3600}{1200} = 3\ \mathrm{m/s^2$}$$

Question 2

Which of the following statements best describes Newton's First Law?

Accepted Answer

An object will remain at rest or move in a straight line at constant speed unless acted upon by a net force.

Question 3

A wind-blown basketball is released from rest in a stiff breeze directed to the right. Which direction does the ball accelerate?

Accepted Answer

Downward and to the right, due to the combination of weight and drag forces.

Question 4

A skier is pulled up a snow-covered hill at constant speed by a rope. What is the net force acting on the skier?

Accepted Answer

$$F_{net} = 0$$

Question 5

A 2-car train travels along a straight track at 40 mph, while a skier speeds up as she skis downhill. On which is the net force greater?

Accepted Answer

The skier

Question 6

A rope lowers an object at constant speed. What is true about the tension in the rope?

Accepted Answer

The rope tension equals the object's weight.

Question 7

A Boeing 737 (mass $$51,000\ \mathrm{kg}) $$accelerates down a runway from rest to takeoff speed over $$940\ \mathrm{m}$$, reaching an acceleration of $$2.61\ \mathrm{m/s^2$}. $$What is the total thrust produced by both engines?

Accepted Answer

$$F = m a = 51,000 	imes 2.61 = 133,110\ \mathrm{N}$$

Question 8

Which of the following is NOT a contact force?

Accepted Answer

Weight

Question 9

A mosquito runs head-on into a truck. Which is true regarding the forces during the collision?

Accepted Answer

The mosquito exerts the same force on the truck as the truck exerts on the mosquito.

Question 10

Which equation correctly expresses Newton's Second Law in vector form?

Accepted Answer

$$\vec{F}_{net} = m \vec{a}$$

Question 11

If the net force on an object is doubled and its mass is quadrupled, what happens to its acceleration?

Accepted Answer

$$a_{new} = \frac{2F}{4m} = \frac{F}{2m}$$

Question 12

Which of the following is a correct statement of Newton's Third Law?

Accepted Answer

For every action, there is an equal and opposite reaction.

Question 13

A person walks forward by pushing backward on the floor with their foot. What force propels the person forward?

Accepted Answer

The static friction force exerted by the floor on the person.

Question 14

Which of the following is the correct SI unit for force?

Accepted Answer

Newton ($$\mathrm{N})$$

Question 15

A free-body diagram for a block sliding down an incline should include which of the following forces?

Accepted Answer

Weight, normal force, and kinetic friction.

Question 16

A rocket launches by expelling hot gases downward. According to Newton's Third Law, what is the reaction force?

Accepted Answer

The gases push the rocket upward.

Question 17

Which of the following is a long-range force?

Accepted Answer

Weight (gravitational force)

Question 18

A block is at rest on a table. Which statement is true about the forces acting on it?

Accepted Answer

The normal force equals the weight of the block.

Question 19

Which of the following best describes the direction of acceleration according to Newton's Second Law?

Accepted Answer

The acceleration points in the same direction as the net force.

Question 20

A spring exerts a force on a mass attached to it. What type of force is this?

Accepted Answer

Contact force

Forces and Newton's Laws: Study Notes for Physics for Life Sciences I (Lecture 7, Sections 4.4-4.8)

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