Answer:
accleraion normal ski 0.0735 m/s², new ski 0.219 m/s²
Explanation:
This exercise should work with the one-dimensional kinetic equations, specifically with the equation
x = v₀ t + ½ a t²
When the skier is at the exit they are at rest, so their initial speed is zero
(v₀ = 0)
x = ½ a t²
Let's calculate the acceleration for normal skiing
a₁ = 2 x / t²
a₁ = 2 175/69²
a₁ = 0.0735 m/s²
a₁ = 7.35 10⁻² m/s²
Let's calculate the acceleration with the new plastic ski
a₂ = 2 x / t₂²
a₂ = 2 175/40²
a₂ = 0.219 m/s²
a₂= 2.19 10⁻¹ m/s²
Answer:
D) - 0.72 secs
Explanation:
Parameters given:
Height of bridge = 40ft = 12.19 m
Initial velocity of Bill's stone = 0m/s
Initial velocity of Ted's stone = 10m/s
We find the time it take Bill's stone to bit the river and the time it takes Ted's stone to hit the river. Then we find the time difference.
Using one of the equations of motion:
For Bill:
S = ut + ½gt²
Where g = 9.8 m/s
12.19 = 0 + ½*9.8*t²
t² = 12.19/4.9 = 2.49
t = 1.58 secs
For Ted:
S = uT + ½gT²
12.19 = 10*T + ½*9.8*T²
=> 4.9T² + 10T - 12.19 = 0
Using quadratic formula and retaining only the positive value, we get that:
T = 0.86 secs
Time difference between Bill's throw and Ted's throw is:
0.86 - 1.58 = - 0.72 secs
In reality, this means that Ted must throw his stone 0.72 secs before Bill throws his for both stones to land the same time.
4. KE increases by a factor of 16 is the answer
<u>Explanation:</u>
Kinetic energy = (1/2)mv² = 0.5 mv²
where
m = mass, and v = velocity.
So at 15 mph,
K
E = 0.5 m (15)
² = 112.5 m
And at 60 mph,
K
E = 0.5 m (60)² = 1800 m
m is the mass, and not meters.
So, 1800 m/112. 5 m = 16
16 times the Kinetic Energy.
Answer: D. 102m
Explanation: Because if you subtract 67m-16m=51. 51 +51 is 102m