Question

A car with a mass of 1.2 × 103 kilograms starts from rest and attains a speed of 20 meters/second in 5 seconds. What net force acted on the car to cause that acceleration?
A.
3.0 × 102 newtons
B.
6.0 × 102 newtons
C.
1.2 × 103 newtons
D.
4.8 × 103 newtons
E.
1.2 × 104 newtons

Answer 1

To find the net force acting on the car, we first need to calculate its acceleration. We can use the formula for acceleration (\(a\)):

\[
a = \frac{\Delta v}{\Delta t}
\]

Where:
- \(\Delta v\) is the change in velocity
- \(\Delta t\) is the change in time

In this case:
- The initial velocity (\(v_i\)) is 0 m/s (the car starts from rest)
- The final velocity (\(v_f\)) is 20 m/s
- The time interval (\(\Delta t\)) is 5 seconds

Now we can calculate the acceleration:

\[
a = \frac{20 \, \text{m/s} - 0 \, \text{m/s}}{5 \, \text{s}} = \frac{20 \, \text{m/s}}{5 \, \text{s}} = 4 \, \text{m/s}^2
\]

Next, we apply Newton's second law to find the net force (\(F\)):

\[
F = m \cdot a
\]

Where:
- \(m\) is the mass of the car (1.2 × 10³ kg)
- \(a\) is the acceleration (4 m/s²)

Now we can calculate the force:

\[
F = (1.2 \times 10^3 \, \text{kg}) \cdot (4 \, \text{m/s}^2) = 4.8 \times 10^3 \, \text{N}
\]

Thus, the net force that acted on the car is:

\[
\boxed{4.8 \times 10^3 \, \text{newtons}}
\]

The correct answer is **D. 4.8 × 10³ newtons**.