Unit 1.3.b - linear motion, angular motion, fluid mechanics and projectile motion

Question 1

Describe how the speed of release and the height of release (if angle and speed of release are
constant) affect the horizontal distance travelled by a projectile. (2)

Answer 1

Speed:
- The faster the speed of release the further the projectile travels
Height:
- The higher the release (compared to landing) the further the projectile travels

(don’t accept reference to angle of release, 45 degrees)

Question 2

Define linear motion and explain how linear motion is created. (2)

Answer 2

• definition – movement in a straight line
• creation - direct force / force applied through centre of mass

Question 3

Identify two factors that affect the horizontal distance travelled by a projectile. (2)

Answer 3

• height of release
• speed/velocity of release
• angle of release
• air resistance/shape of object/spin of the object

Question 4

Fig.3 shows a gymnast performing a back somersault.

Explain how angular velocity is controlled by the gymnast during take-off, flight and landing. (6)

Answer 4

• Newton 1st law: A body will continue to rotate with constant angular
  momentum unless acted upon by an external torque/moment
• (momentum) Principle of conservation of angular momentum
• angular momentum = moment of inertia x angular velocity
• (take-off) gymnast generates angular momentum off floor
• Moment of inertia (MI) high as body is extended
• therefore angular velocity (w) / rate of spin is low
• (flight) MI is reduced as body is tucked
• therefore angular velocity / rate of spin increases
• (entry) MI is increased as body is extended
• therefore angular velocity / rate of spin is reduced
• to prevent over rotation / controlled landing