Rigidbody2D component in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Rigidbody2D velocity change?

Consider a Rigidbody2D with initial velocity (2, 3). After running the code below, what will be the new velocity?

Unity

Rigidbody2D rb = GetComponent<Rigidbody2D>();
rb.velocity = new Vector2(5, rb.velocity.y);

A (5, 3)

B (2, 3)

C (5, 0)

D (0, 3)

💡 Hint

Remember that only the x component of velocity is changed.

The code sets the x velocity to 5 but keeps the y velocity unchanged at 3.

🧠 Conceptual

intermediate

Which Rigidbody2D property controls gravity effect?

Which property of Rigidbody2D determines how much gravity affects the object?

A gravityScale

B mass

C drag

D angularVelocity

💡 Hint

Think about the property that scales gravity force.

gravityScale multiplies the global gravity to control how strongly gravity affects the Rigidbody2D.

🔧 Debug

advanced

Why does this Rigidbody2D not move as expected?

Given this code, the Rigidbody2D does not move when applying velocity. What is the likely cause?

Unity

Rigidbody2D rb = GetComponent<Rigidbody2D>();
rb.velocity = new Vector2(10, 0);

A The Rigidbody2D mass is zero

B The Rigidbody2D has no Collider2D

C The velocity vector is zero

D The Rigidbody2D is set to 'Is Kinematic' true

💡 Hint

Check Rigidbody2D settings that disable physics movement.

If 'Is Kinematic' is true, Rigidbody2D ignores velocity and physics forces, so it won't move automatically.

📝 Syntax

advanced

Which code correctly applies a force to Rigidbody2D?

Choose the correct syntax to add a force of (0, 10) to a Rigidbody2D named rb.

A rb.AddForce = new Vector2(0, 10);

B rb.AddForce(new Vector2(0, 10));

C rb.AddForce(Vector2(0, 10));

D rb.AddForce(new Vector3(0, 10, 0));

💡 Hint

Remember the method signature and vector type for 2D physics.

AddForce expects a Vector2 argument. Option B uses correct syntax and vector type.

🚀 Application

expert

How to freeze Rigidbody2D rotation but allow movement?

You want a Rigidbody2D to move freely but never rotate. Which code snippet achieves this?

A rb.isKinematic = true;

B rb.freezeRotation = true;

C rb.constraints = RigidbodyConstraints2D.FreezeRotation;

D rb.constraints = RigidbodyConstraints2D.FreezePositionX | RigidbodyConstraints2D.FreezePositionY;

💡 Hint

Look for Rigidbody2D constraints that affect rotation only.

Setting constraints to FreezeRotation stops rotation but allows position movement.