Jenny and Alyssa are members of the cross-country team. On a training run, Jenny starts off and runs at a con-stant 3.8 m/s. Aly
1 answer:
Answer:Answer:
300 seconds
Explanation:
We solve this problem using the equation of uniform motion;
d =v*t
d: Distance traveled
t: Time
v: Speed
We raise the equations of uniform motion because they run at a constant speed.
dJ=3.8*tJ Motion equation for Jenny
dA=4*tA Motion equation for Alyssa
d:distancia
When Jenny and Alissa meet, they will have traveled the same distance,then:
dJ=dA
3.8 tJ =4*tA
tA = * tJ
tA =0.95¨*tJ Equation (1)
Jenny runs 15 seconds longer than Alyssa,then:
tJ = tA+15 Equation (2)
We replace tA =0.95tJ of the Equation (1) in the Equation (2):
tJ = 0.95*tJ +15
tJ-0.95*tJ=15
0.05* tJ=15
tJ=
tJ=300 s
Alyssa catch up with Jenny in 300 s after Jenny’s start .
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with negative sign, because it is directed downward.
To find the velocity, we should compute the derivative of h(t):
So now we can calculate the speed at t=2 s and t=4 s:
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2) The projectile reaches its maximum height when the speed is equal to zero:
So we have
And solving this we find
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4) The time at which the projectile hits the ground is the time at which the height is zero: h(t)=0. So, this translates into
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And this is the time at which the projectile hits the ground.
5) The velocity of the projectile when it hits the ground is the velocity at time t=4.68 s:
with negative sign, because it is directed downward.
Answer is: 1973.17N aprox.
step by step in the pic below
step by step in the pic below