Q: A worker pushes a crate of mass $$M on a $$frictionless surface with a force $$P at an $$angle $$\theta$$ above the horizontal. What is the acceleration $$a of $$the crate?

$$a = \frac{P \cos \theta}{M}$$

Question 1

Which statement best describes Newton's 1st Law of Motion?

Accepted Answer

An object will remain at rest or move with constant velocity unless acted upon by a nonzero force.

Question 2

A ball is thrown straight up. Disregarding air resistance, what force acts on the ball while it is in the air?

Accepted Answer

A constant downward force of gravity.

Question 3

Which of the following is NOT a type of force listed in the lecture?

Accepted Answer

Thermal force

Question 4

What is inertia?

Accepted Answer

The resistance of an object to changes in its motion.

Question 5

Which equation correctly represents Newton's 2nd Law?

Accepted Answer

$$\sum \vec{F} = m \vec{a}$$

Question 6

A crate of mass $$M is $$pushed on a frictionless surface with a force $$P at an $$angle $$	heta$$ above the horizontal. What is the expression for the normal force $$N$$ acting on the crate?

Accepted Answer

$$N = Mg - P \sin 	heta$$

Question 7

If a net force acts on a body, what happens to the body according to Newton's 2nd Law?

Accepted Answer

It accelerates in the direction of the net force.

Question 8

What is the weight $$W of an $$object of mass $$m at $$Earth's surface?

Accepted Answer

$$W = m \vec{g}$$

Question 9

In an elevator accelerating upwards with acceleration $$a$$, what is the apparent weight $$N of a $$person of mass $$M$$?

Accepted Answer

$$N = M(g + a)$$

Question 10

Which of the following is true about free fall acceleration near Earth's surface?

Accepted Answer

It is independent of the mass of the object.

Question 11

A ball rolls to the back of an airplane during take-off. What does this indicate about the airplane's reference frame?

Accepted Answer

It is not an inertial reference frame.

Question 12

Which of the following is a correct procedure for solving force problems?

Accepted Answer

Draw a free-body diagram, choose a coordinate system, write out force components, and solve symbolically.

Question 13

If the cable of an elevator breaks and the elevator is in free fall, what is the normal force $$N$$ acting on a person inside?

Accepted Answer

$$N = 0$$

Question 14

Which of the following best describes a force?

Accepted Answer

A push or pull that acts on an object and has magnitude and direction.

Question 15

A spring scale measures which force when you stand on it?

Accepted Answer

Normal force

Question 16

Which equation represents the component form of Newton's 2nd Law in the x-direction?

Accepted Answer

$$\sum F_x = m a_x$$

Question 17

If an object is moving with constant velocity, what can be said about the net force acting on it?

Accepted Answer

The net force is zero.

Question 18

Which of the following is a long-range force?

Accepted Answer

Gravity

Question 19

A worker pushes a crate of mass $$M on a $$frictionless surface with a force $$P at an $$angle $$	heta$$ above the horizontal. What is the acceleration $$a of $$the crate?

Accepted Answer

$$a = \frac{P \cos 	heta}{M}$$

Question 20

Which transformation shows that Newton's Laws look the same in all inertial reference frames?

Accepted Answer

Galilei Transformation

Newton's First and Second Laws: Inertia, Forces, and Problem Solving

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