Answer:
contact
Explanation:
A contact force is defined as a force which requires some contact to occur. When we apply force that is in contact with the objects are called as contact forces.
In the context, Carmen is loading furniture and boxes on a moving van by picking up by picking up the boxes or furniture on a cart and pushing it onto the van. Carmen uses contact forces to lift the boxes and furniture onto the van.
1) 
We can solve this part by using Newton's second law:
(1)
where
F is the net force
m is the mass
a is the acceleration
There are two forces acting on the boat:
forward
backward
So the net force is

We know that the mass of the boat is
m = 1177.5 kg
So we can now use eq.(1) to find the acceleration:

2) 161.0 m
We can solve this part by using the following suvat equation:

where
s is the distance travelled
u is the initial velocity
t is the time
a is the acceleration
Here we have
u = 0 (the boat starts from rest)

Substituting t = 17.7 s, we find the distance covered:

3) 18.2 m/s
The speed of the boat can be found with the following suvat equation

where
v is the final velocity
u is the initial velocity
t is the time
a is the acceleration
In this case we have
u = 0 (the boat starts from rest)

And substituting t = 17.7 s, we find the final velocity:

And the speed is just the magnitude of the velocity, so 18.2 m/s.
Answer:
560 m
Explanation:
The speed of sound in air is approximately:
v ≈ v₀ + 0.6T
where v₀ is the speed of sound at 0°C (273 K) in m/s, and T is the temperature in Celsius.
The speed of sound at 20°C at that altitude is:
v ≈ 327 + 0.6(20)
v ≈ 339 m/s
The sound travels from the hikers to the mountain and back again, so it travels twice the distance.
339 m/s = 2d / 3.3 s
2d = 1118.7 m
d = 559.35 m
Rounding, the mountain is approximately 560 m away.
The answer would be C. The gravitational force between two bodies however it is too small that it is overshadowed by that of earth. Gravitational force is the weakest force of all. Each body with a mass exerts a gravitational force onto each other but this value is so small that it can be neglected.