Physics materials (friction, bounce) in Unity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of the friction value?

Consider a Unity Physics Material with dynamic friction set to 0.5 and static friction set to 0.7. If you print the dynamic friction value in a script, what will be the output?

Unity

using UnityEngine;

public class FrictionTest : MonoBehaviour {
    public PhysicMaterial mat;
    void Start() {
        Debug.Log(mat.dynamicFriction);
    }
}

A 0.7

B 0.5

C 1.0

D 0.0

💡 Hint

Remember dynamic friction is different from static friction.

The dynamic friction value is 0.5 as set in the Physics Material. Static friction is a separate property and does not affect this output.

❓ Predict Output

intermediate

What happens when bounce is set to 1?

In Unity, if a Physics Material has bounciness set to 1 and bounce combine set to Maximum, what will happen when a ball hits a surface with this material?

A The ball will bounce back with the same energy it hit with.

B The ball will not bounce at all.

C The ball will bounce but lose half its energy.

D The ball will stick to the surface.

💡 Hint

Bounciness of 1 means no energy loss on bounce.

A bounciness of 1 means the ball bounces back with full energy, so it will bounce back to the original height.

❓ Predict Output

advanced

What is the friction value used during collision?

Two objects collide in Unity. Object A has a Physics Material with dynamic friction 0.4 and static friction 0.6. Object B has dynamic friction 0.8 and static friction 0.9. The friction combine mode is set to Multiply. What is the dynamic friction used during collision?

A 1.0

B 0.6

C 0.8

D 0.32

💡 Hint

Multiply means multiply the two friction values.

Dynamic friction used is 0.4 * 0.8 = 0.32 when combine mode is Multiply.

❓ Predict Output

advanced

What is the resulting bounce when combine mode is Maximum?

If two Physics Materials collide, one with bounciness 0.3 and the other with 0.7, and the bounce combine mode is set to Maximum, what is the resulting bounce value used?

A 1.0

B 0.3

C 0.7

D 0.5

💡 Hint

Maximum means the higher bounce value is used.

The bounce combine mode Maximum uses the higher of the two bounciness values, which is 0.7.

🧠 Conceptual

expert

Which Physics Material setting causes an error?

Which of the following Physics Material settings will cause a runtime error or unexpected behavior in Unity?

A Setting dynamic friction to -0.1

B Setting friction combine mode to 'Average' and bounciness to 0.5

C Setting bounciness to 1.0 and friction combine to 'Multiply'

D Setting static friction to 0.0 and bounciness to 0.0

💡 Hint

Friction values cannot be negative.

Negative friction values are invalid and cause unexpected behavior or errors in Unity physics.