Q: Which of the following is the correct expression for Newton's second law in vector form?

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

Question 1

A block is pushed across a horizontal table at a constant speed. Which statement best describes the relationship between the pushing force and the friction force?

Accepted Answer

The pushing force is equal in magnitude and opposite in direction to the friction force.

Question 2

A skier is being towed up a snow-covered hill at constant speed. Which forces act on the skier?

Accepted Answer

Tension, normal force, weight, and kinetic friction.

Question 3

Which of the following is the correct expression for Newton's second law in vector form?

Accepted Answer

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

Question 4

A ball is tossed straight up. Just after it leaves the hand (ignoring air resistance), which force(s) act on it?

Accepted Answer

Only the weight of the ball acting downward.

Question 5

A 10 kg object is subjected to a net force of 50 N. What is its acceleration?

Accepted Answer

$$a = 5\ 	ext{m/s}^2$$

Question 6

A steel beam hangs from a cable as a crane lifts the beam. What forces act on the beam?

Accepted Answer

Gravity and tension in the cable.

Question 7

A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she’s jumped in?

Accepted Answer

Gravity, a normal force, and kinetic friction.

Question 8

A Boeing 737 with a mass of $$51,000\ 	ext{kg}$$ accelerates from rest to $$70\ 	ext{m/s}$$ over a distance of $$940\ 	ext{m}. $$What is the magnitude of the net force (thrust) acting on the plane during takeoff? (Assume constant acceleration.)

Accepted Answer

$$133,000\ 	ext{N}$$

Question 9

A cart is pulled to the right with a constant, steady force. How will its acceleration graph look?

Accepted Answer

Acceleration is constant over time.

Question 10

A ball rolls down an incline and off a horizontal ramp. Ignoring air resistance, what force or forces act on the ball as it moves through the air just after leaving the ramp?

Accepted Answer

The weight of the ball acting vertically down.

Question 11

A block is at rest on a frictionless surface. If a constant force is applied, what will happen to its velocity?

Accepted Answer

It will increase linearly with time.

Question 12

A 2 kg object experiences a net force of 8 N. What is its acceleration?

Accepted Answer

$$a = 4\ 	ext{m/s}^2$$

Question 13

A 1 kg mass is accelerated at $$1\ 	ext{m/s}^2. $$What is the force required to produce this acceleration?

Accepted Answer

$$1\ 	ext{N}$$

Question 14

A car is parked on a hill. Which force is responsible for preventing the car from sliding down?

Accepted Answer

Static friction.

Question 15

A rocket expels exhaust gases downward. What is the direction of the thrust force acting on the rocket?

Accepted Answer

Upward, opposite to the direction of the expelled gases.

Question 16

A person stands on a bathroom scale in an elevator that is accelerating upward. How does the normal force (reading on the scale) compare to the person's weight?

Accepted Answer

The normal force is greater than the person's weight.

Question 17

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

Accepted Answer

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

Question 18

A rope is used to lower an object at a steadily decreasing speed. Which statement is true about the tension in the rope compared to the object's weight?

Accepted Answer

The rope tension is less than the object's weight.

Question 19

Which of the following is a long-range force?

Accepted Answer

Gravity.

Forces and Newton's Laws of Motion: Study Notes

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