The cart comes to rest from 1.3 m/s in a matter of 0.30 s, so it undergoes an acceleration <em>a</em> of
<em>a</em> = (0 - 1.3 m/s) / (0.30 s)
<em>a</em> ≈ -4.33 m/s²
This acceleration is applied by a force of -65 N, i.e. a force of 65 N that opposes the cart's motion downhill. So the cart has a mass <em>m</em> such that
-65 N = <em>m</em> (-4.33 m/s²)
<em>m</em> = 15 kg
Answer:
drag force 
Velocity (V) = 40.169 m/s
Explanation:
The drag force
is given by the formula:

where:
= drag coefficient depending on the Reynolds number
Reynolds number Re = 
Let's Assume that the air is in room temperature at 25 °C ; Then
density of the air
= 1.1845 kg/m³
viscosity of fluid or air
= 1.844 × 10⁻⁵ kg/ms
diameter of the baseball D = 7.4 cm
Velocity V = 44.3 m/s
Replacing them into the equation of Reynolds number ; we have :

A = Projected Area
From the diagram attached below which is gotten from NASA for baseball;
the drag coefficient which depends on Reynolds number is read as:
= 0.3
Projected Area A = 
A = 
A = 0.0043 m²
Finally, drag force is then calculated as ;

b)

since acceleration a = 
Then;

Also;
velocity (V) = 
Then;



Then;


Integrating the above equation ; we have :

when time (t) = 0 ; then 
44.3 = - 10 × 0 + C
C = 44.3

Time (t) =

∴ Velocity ; 

Velocity (V) = 40.169 m/s
I'm pretty sure it's D. negative acceleration
... The torpedo gets 20m farther away every second.
... After 100s, it's 2,000m away.
... It explodes.
... They hear it 101.4s after it was launched.
... That's 1.4s after the explosion.
... The sound covered the 2,000m back to them in 1.4 sec.
Speed = distance / time
= 2000m / 1.4s = 1,428.6 m/s (rounded)