Question

Consider two cars moving along the same straight road in opposite directions. Car A has a mass of 500kg and has a constant speed of 20m/s; car B has a mass of 800kg and a constant speed of 15m/s. What can you say about the net forces on the cars? 1. Car A experiences greater net force than car B.2. Car B experiences greater net force than car A.3. Both cars experience equal net forces.

Answer 1

Answer:

3. Both cars experience equal net forces.

Explanation:

According to Newton's 1st law, object subjected to 0 force, or net force equals 0, would be at rest or maintain a constant speed. In our cases both cars are at constant speed (whatever they are) so each of their individual net force must be 0. Both cars experience equal net forces.

Answer 2

Answer:

3. Both cars experience equal net forces

Explanation:

The net force (∑F) on a body, according to Newton's second law of motion, is the product of the mass (m) of the body and the acceleration (a) of motion of the body. This can be written mathematically as follows;

∑F = m x a       -----------------------(i)

Given;

Car A => mass = 500kg and constant speed = 20m/s

Car B => mass = 800kg and constant speed = 15m/s

Both cars are moving at constant speed. This means that the velocities of the two cars are not changing. i.e

For Car A, initial velocity (u) = 20m/s and final velocity (v) =  20m/s. Hence acceleration which is a time rate of change in velocity is zero;

i.e

a = (v - u) / t

a = (20 - 20) / t = 0

For Car B, initial velocity (u) = 15m/s and final velocity (v) =  15m/s. Hence acceleration which is a time rate of change in velocity is zero;

i.e

a = (v - u) / t

a = (15 - 15) / t = 0

Therefore, the accelerations of both cars are zero (0). In other words, constant speed means zero acceleration.

Now, let's calculate the net force on Car A;

∑F = m x a        [where m = 500kg, a = 0]

∑F = 500 x 0

∑F = 0 N

Also, let's calculate the net force on Car B;

∑F = m x a        [where m = 800kg, a = 0]

∑F = 800 x 0

∑F = 0 N

Therefore, both cars experience equal net forces of zero (0);