Question 1

A 10 kg crate is pushed along a horizontal surface at a constant velocity of 2 m/s. What is the rate of change of the crate's momentum?

Accepted Answer

$$0\ \mathrm{kg\cdot m/s^2$}$$

Question 2

Which of the following best describes the relationship between force, change in momentum, and time interval?

Accepted Answer

$$F \propto \Delta p / \Delta t$$

Question 3

A car travels down a slope at a constant speed. What is the vector sum of all forces acting on the car?

Accepted Answer

Zero.

Question 4

During a collision between a mosquito and a bus, which statement is true about the magnitude of the change in momentum for each?

Accepted Answer

The mosquito's change in momentum is equal to the bus's.

Question 5

Which of the following is NOT an example of a field force?

Accepted Answer

Frictional force

Question 6

A book rests on a table. Which of the following statements is correct?

Accepted Answer

The vector sum of the forces on the book is zero.

Question 7

Which of the following is the correct equation for the vector sum of forces acting on an object in terms of its momentum?

Accepted Answer

$$\sum \vec{F} = \frac{d\vec{p}}{dt}$$

Question 8

A person is sitting on a stool in a lift. The forces exerted on the stool are: 60 N downward by Earth, 780 N downward by the person, and 850 N upward by the lift floor. If the stool's mass is 5.0 kg, what is the acceleration of the lift?

Accepted Answer

$$2.0\ \mathrm{m/s^2$}$$

Question 9

Which of the following best describes Newton's Third Law?

Accepted Answer

Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction.

Question 10

A spring is stretched by a force $$F$$ and its displacement from equilibrium is $$x. $$What is the spring constant $$k$$ according to Hooke's Law?

Accepted Answer

$$k = F/x$$

Question 11

If a force is applied to a cart for twice as long, how does the change in momentum compare to applying the same force for the original time?

Accepted Answer

It is twice as large.

Question 12

A constant force is exerted for a short time interval on a cart initially at rest. The same force is exerted for the same time on another cart with twice the mass. The final speed of the heavier cart is:

Accepted Answer

Half that of the lighter cart.

Question 13

Which of the following is true about the forces in an interaction pair?

Accepted Answer

They are equal in magnitude and opposite in direction.

Question 14

A rope is used in a tug-of-war. If two people pull on opposite ends with force $$F$$, what is the tension in the rope?

Accepted Answer

$$F$$

Question 15

Which of the following is the SI unit of force?

Accepted Answer

kg·m/s²

Question 16

A spring with a large spring constant $$k is$$:

Accepted Answer

Stiffer than a spring with a small $$k.$$

Question 17

Which of the following best describes impulse?

Accepted Answer

Impulse is the change in momentum of a system during a period.

Question 18

A book is dropped from a height. How does the magnitude of the force exerted by the book on Earth compare to the force exerted by Earth on the book?

Accepted Answer

The forces are equal in magnitude.

Question 19

A constant force is exerted on a cart initially at rest. If the force is halved, how long must it be applied to reach the same final speed?

Accepted Answer

Twice as long.

Chapter 8: Force – Foundations of Dynamics

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