Biomechanics: Applying forces in sport

Question 1

What are the vertical forces (components)?

Answer 1

• Weight (W) is a gravitational force (downwards).
• Ground reaction force (GRF).

Question 2

What are the horizontal forces (components)?

Answer 2

• Friction (F).
• Air resistance (AR)= also known as drag!

Question 3

What are the paired forces? (Newton’s 3rd law)

Answer 3

• Action force.
• Reaction force.

Question 4

Look at the rectangles for long jumpers and high jumpers!!!!

Question 5

What are balanced forces?

Answer 5

• Occur when two or more forces are in operation that are equal in size but opposite in direction.
• Because all forces cancel each other out the net force is zero.
• A ball sat on the floor, or a sprinter running at a constant speed.

Question 6

What are unbalanced forces?

Answer 6

• Occur when a force acting in one direction is larger than the one acting in the other (direction).
• This will cause acceleration or deceleration in one direction (2nd law) once overcoming inertia (1st law).

Question 7

What are resultant forces?

Answer 7

• This is basically the outcome of two forces meeting.
• Zero= balanced.
• Positive= acceleration.
• Negative= deceleration.

Question 8

What is friction?

Answer 8

• Friction acts in opposition to motion.
• Running= friction is going forwards whilst running (a foot pushes backwards to go forwards).
• Athletes and sporting bodies actually want to generate more friction most of the time:
  1. Spikes.
  2. Studs.
  3) Playing surfaces.
  4) Tires.

Question 9

Free body diagram tips

Answer 9

1. The length of the arrow reflects the size of the force.
2. Draw a direction of motion arrow.
3. Add vertical forces- weight and ground reaction force.
4. Add horizontal forces- air resistance and friction.
5. Add paired forces- action force/ reaction force.

Question 10

Free body diagrams tips (pt.2)

Answer 10

6. Mention resultant forces- accel/ decel/constant.
7. The weight force (W) is always drawn from the centre of mass.
8. The reaction force (R) or ground reaction force (GRF) starts from where two bodies are in contact with another. Foot and the ground (GRF) or between sports equipment (tennis racket and ball).
9. The friction force (F) starts from where two bodies are in contact and is opposite to the direction of potential slipping. It is usually drawn in the same direction as motion.
10. Air resistance (AR) is drawn from the centre of mass and opposes the direction of the body.