B. Closed because otherwise the energy would "escape"
Answer:
Initial velocity (u) = 40 m/s
Distance travel in last 5 seconds = 100 m
Explanation:
Given:
Acceleration (a) = 8 m/s²
Final velocity (v) = 0 m/s
Find;
1] Initial velocity before 5 sec
2] Distance travel in last 5 seconds
Computation:
1] Initial velocity before 5 sec
v = u + at
0 = u + (-8)(5)
u - 40 = 0
Initial velocity (u) = 40 m/s
2] Distance travel in last 5 seconds
s = ut + (1/2)(a)(t²)
s = (40)(5) + (1/2)(-8)(5²)
s = 200 - 100
Distance travel in last 5 seconds = 100 m
Answer:
d) The total mechanical energy is constant.
Explanation:
The total mechanical energy of a pendulum is given by:
where
KE is the kinetic energy (the energy of motion), given by
where
m is the mass of the pendulum
v is its speed
PE is the potential energy of the pendulum (the energy due to its position), given by
where
g is the acceleration due to gravity
h is the height of the pendulum relative to the ground
In absence of air resistance, the total mechanical energy of the pendulum is constant. This means that there is a continuous conversion of energy between kinetic and potential. In particular:
- When the pendulum is at its highest position (maximum displacement), the potential energy is maximum while the kinetic energy is minimum)
- When the pendulum crosses its equilibrium position, the kinetic energy is maximum (maximum speed) while the potential energy is minimum
Answer:
The coefficient of restitution is greater in a head-on collision
Explanation:
Let m be the masses of the electric vehicles and v be their initial speeds. Since they are moving in opposite directions, the momentum, p₁ of the first electric vehicle = mv and that of the second vehicle is p₂ = -mv. Let p₃ and p₄ be their final momenta. From the law of conservation of momentum, momentum before impact = momentum after impact.
So, p₁ + p₂ = p₃ + p₄
mv + (-mv) = p₃ + p₄
mv - mv = p₃ + p₄
0 = p₃ + p₄
p₃ = -p₄
mv₃ = -mv₄
v₃ = -v₄. where v₃ and v₄ are their final velocities. This shows that their final velocities are not zero. So they do not come to a stop.
Now, we calculate the coefficient of restitution, e = -(v₄ - v₃)/(v₂ - v₁) = -(v₄ -
(-v₄))/(-v - (v))= - (v₄+ v₄)/-(v + v) = 2v₄/2v = v₄/v. Since e ≠ 0, the vehicles do not come to a stop
Head-on collisions are more jarring because, the coefficient of restitution is greater in an head-on collision because, the maximum value of the velocity is used by the electric vehicles. They only have velocity components in one direction, thereby, having a maximum value for the coefficient of restitution.