Vectors, force and Newton's Second Law
Vectors, force and Newton's Second Law
In sessions earlier in the unit you will have met the idea of vectors.
Force is a vector quantity as it has properties of magnitude and direction.
You should recall (see lecture notes if you have forgotten!) that vectors
can be manipulated mathematically in a number of ways. Of particular importance
are the ideas of working out components when given a resultant and the
reverse process of calculating a resultant when given components. The
following questions focus on manipulating vectors in these two contexts
and then relating them to the principles embedded in Newton's Second Law.
Some of the questions are not directly related to vertical jumping but
a key idea to understand is that vertical forces must be determined when
vertical motion is to be explained. These questions get you to think of
movement in terms of vertical and horizontal motion.
1. A force of 1000 N was applied at an angle of 70° to the horizontal at one instant during a standing broad jump.. What proportion of the force was applied vertically and what proportion of the force was applied a horizontally.
2. During a volleyball block technique it is known that an 80 kg player experienced a vertical ground reaction force of 1200 N. Taking acceleration due to gravity to be 9.81 ms-2 , calculate the acceleration experienced by the volleyball player at this moment in time. (Clue: You need to work out the net acceleration by first calculating the net force).
3. During the take off at the start of the hop phase of a triple jump a 72kg athlete experiences a ground reaction force of 1600 N acting at an angle of 75° to the horizontal in a forward direction. Taking acceleration due to gravity to be 9.81 ms-2 and, ignoring air resistance, calculate the horizontal and vertical acceleration experienced by the jumper at this point in time.
