Athelete jump finding starting speed

[mortho]

An athlete executing a long jump leaves the ground at a 40° angle and travels 6.30 m.

a) what was the take off speed?
b) If the speed was increased by just 4.0 percent, how much longer would the jump be?

** i used squareroot of 2ax to find initial velocity and got 8.91 m/s but got it wrong. what was the problem>?

 

[dynamicsolo]

An athlete executing a long jump leaves the ground at a 40° angle and travels 6.30 m.

a) what was the take off speed?
b) If the speed was increased by just 4.0 percent, how much longer would the jump be?

** i used squareroot of 2ax to find initial velocity and got 8.91 m/s but got it wrong. what was the problem>?

Since the jumper is traveling in two dimensions (vertically as well as horizontally), you cannot simply use the "velocity-squared" formula to find their starting speed.

The jumper takes on with an unknown speed v0 at a 40º angle to the horizontal. What does that mean for their starting horizontal and vertical velocities? How long will the jumper stay in the air before landing? You are told how far they moved horizontally before touching down.

Once you have part (a), that will give you an idea of how to deal with part (b).