Question

Please Help! Question 2 Unsaved

Which has the most inertia?

Question 2 options:

a sports car going 210 mph around the track


your pet dog/cat/horse/bird/fish moving at their fastest speed


a cruise ship docked in a port


a pebble travelling through space at 90,500,000 km/s

Question 3 Unsaved
What unit must be used when measuring mass?

Question 3 options:

gram


pound


liter


seconds


What unit is used for acceleration?

Question 4 options:

m/s


m/s2


ft/min


none of the above

Question 5 Unsaved
What unit do we use for force?

Question 5 options:

pounds


Galileos


Newtons


none of the above

Question 6 Unsaved
How much force is necessary when Gretzky accelerates a 1.04 kg hockey puck at 987 m/s2?

Question 6 options:

0.01 N


94.9 N


1030 N


none of the above

Question 7 Unsaved
The acceleration of The Munster’s car is 9.71 m/s2 when he applies 5050 N of net force (by way of the engine). What is the mass of his car in kilograms?

Question 7 options:

520 kg


49,000 kg


0.0019 kg


none of the above

Amber applies a net force of 35 N to pull her younger brother (32 kg) in a wagon (3 kg). At what rate does the wagon accelerate?

Question 8 options:

1.09 m/s2


0.91 m/s2


1.00 m/s2


It doesn't accelerate
Question 9 Unsaved
When a car stops suddenly, the groceries in the trunk tend to keep moving

Question 9 options:

backward


forward


to the left


to the right

Question 10 Unsaved
Which of the following defines inertia?

Question 10 options:

The tendency of an object with mass to resist a change in its motion.


The tendency of mass not to resist any change in its motion.


The tendency of a mass-less object to resist a change in its motion.


The tendency of objects to speed up or slow down.


The tendency of an object with a weight to resist a change in its motion.

Answer 1

2. a cruise ship docked in a port

In fact, inertia is the resistance of an object to any change in its velocity/change of its state of motion. The inertia of an object depends only on the mass of the object: the greater the mass, the larger the inertia. In this case, the object with largest mass among the choices is the cruise ship docked in the port, so this is the object with most inertia.

3. gram

Mass represents the quantity of matter inside an object, and it is measured in grams (g). Actually, the SI units of the mass is the kilogram (kg), a multiple of the gram: 1 kg = 1000 g.

4.
`m/s^2`

Acceleration is defined as the rate of change of velocity per unit time:

`a=(\Delta v)/(\Delta t)`

The change in velocity,
`\Delta v`, is measured in m/s, while the time
`\Delta t` is measured in seconds (s): therefore, the acceleration is measured in

`[a]=([m/s])/([s])=[(m)/(s^2)]`

5. Newtons

The Newton (N) is the SI unit used for the force. The force is defined as the product between mass (m) and acceleration (a):

`F=ma`

since the mass is measured in kg and the acceleration in m/s^2, 1 Newton corresponds to

`1 N= 1 kg (m)/(s^2)`

6. 1030 N

Given m=1.04 kg (mass of the hockey puck) and
`a=987 m/s^2` (acceleration of the hockey puck), the force needed to accelerate the puck with this acceleration is given by Newton's second law:

`F=ma=(1.04 kg)(987 m/s^2)=1026 N`

which corresponds (approximately) to option C) 1030 N.

7. 520 kg

Given
`a=9.71 m/s^2` (acceleration of the car) and F=5050 N (net force applied on the car), we can find the mass of the car by using again Newton's second law:

`m=(F)/(a)=(5050 N)/(9.71 m/s^2)=520 kg`

8. 1.00 m/s2

In this case, the net force applied by Amber is F=35 N.

The total mass of the brother+wagon is

`m=32 kg+3 kg=35 kg`

Therefore, we can find the acceleration of the system by using again Newton's second law:

`a=(F)/(m)=(35 N)/(35 kg)=1.00 m/s^2`

9. forward

This is because of the inertia: in fact, the car (and the groceries inside it) is initially moving forward. When it stops, the groceries inside the car tends to continue moving forward: due to their inertia, they tends to continue their motion with constant speed, until they are stopped by an external force.

10. The tendency of an object with mass to resist a change in its motion.

Inertia is exactly this: the tendency of an object with mass to resist a change in its motion. This means that an object at rest tends to stay at rest, while an object in motion tends to keep its speed. The inertia of an object depends only on its mass: the larger the mass, the greater the inertia.