Calculating Velocity and Distance in One-Dimensional Motion

[chawki]

Homework Statement

The mass of a van with a driver is 2000 kg . When the van accelerates, the velocity increases
with a uniform acceleration of 3.0 m/s².

Homework Equations

a) The van starts at rest. Find the velocity after 4.0 s.
b) How far does the van travel in the first 4.0 s?
c) Find the acceleration when an additional load of 1200 kg is added onto the van. Assume
that the accelerating force remains unchanged.

The Attempt at a Solution

a)
V=a*t+V₀
V0=0
so: V=3*4=12.0 m/s
b)
V²-V₀²=2*a*x
x=v²/2*a
x=12²/6
x=24m.
so he traveled 24m.
c)
F=m*a
a=F/3200
and we don't have F

 

[member 198005]

What would happen to the acceleration of the truck if you added the weight? Why?

EDIT: I see it says it explicitly in part C. The accelerating force remains unchanged.

 

[chawki]

probaly the acceleration would get reduced?

 

[member 198005]

Correct. Because the force stays constant the acceleration will decrease if the mass increases. Intuitively you already know the force doesn't change. Therefore, you do in fact know what F is.

 

[chawki]

F=m₁*a₁ ?
F=2000*3=6000N.

and then a₂=F/m₂
a₂=6000/3200=1.875m/s² ?

 

[member 198005]

Correct!

 

[chawki]

Thank you