Question

a student is analyzing the forces on a 400 kg car driving at a constant velocity of 20 m/s. they draw the following diagram: which of the following statements properly identifies what is wrong with their force diagram? a. the forward force should be 20 n rather than 8,000 n since f = ma. b. the diagram shows a net force but there should not be a net force on the car. c. there cannot be any forces on the car if it has a constant velocity so there should be no arrows. d. there should be more backward force on the car because the car is slowing down.

Explanation:

Step1: Analyze Newton's first law

When an object moves at a constant velocity, the net force acting on it is zero according to Newton's first law.

Step2: Check each option

• Option A: Since \(a = 0\) (constant velocity), \(F=ma = 0\), not \(F = 20N\). So this option is wrong.
• Option B: The diagram shows only a forward force, implying a net force. But for constant - velocity motion (\(a = 0\)), net force \(F_{net}=0\). This option is correct.
• Option C: There are forces on the car (e.g., gravitational force, normal force, forward force from engine, backward frictional force). Just their vector sum is zero. So this option is wrong.
• Option D: The car is moving at a constant velocity, not slowing down. So there is no reason for more backward force. This option is wrong.

Answer:

B. The diagram shows a net force but there should not be a net force on the car.