because the car returned to A the velocity is 0
D. The velocity is zero but the speed
Answer:
v_y = v_{oy} - g t
where the upward direction is positive, so the arrow represents this speed (blue) must decrease, reach zero and grow in a negative direction as time progresses
Explanation:
In this exercise you are asked to observe the change in velocity in a projectile launch.
If we assume that the friction force is small, the velocity in the x-axis must be constant
vₓ = v₀ₓ
Therefore, the arrow (red) that represents this movement must not change in magnitude.
In the direction of the y axis, the acceleration of gravity is acting, so the magnitude of the velocity in this axis changes
v_y = v_{oy} - g t
where the upward direction is positive, so the arrow represents this speed (blue) must decrease, reach zero and grow in a negative direction as time progresses
Answer:
A The force of air resistance becomes equal in magnitude to his weight.
Explanation:
When Carlos jumped out of the helicopter, he fell with a downward force which is proportional to his weight.
His weight is the product of his mass and acceleration due to gravity.
When the parachute is deployed, air resistance between the air molecules and the surface area of the parachute generates a drag force, which acts upwards.
If the drag forces exceeds his weight, then his net force will be directed upwards.
If his weight exceeds the drag forces, then the net force on his body will be downwards.
In the case that his drag force, and his weight are equal, there will be a zero net force on him, and he will experience no acceleration.
So, if after he opens his parachute, his acceleration due to gravity decreases to zero, then we can say that this is because the force of air resistance (drag) becomes equal in magnitude to his weight.
Answer:
Oil : about 50years
Gas: about 52years
Coal: about 114years
Explanation:
Oil
Globally, we currently consume the equivalent of over 11 billion tonnes of oil from fossil fuels every year. Crude oil reserves are vanishing at a rate of more than 4 billion tonnes a year, so if we carry on as we are, our known oil deposits could run out in just about 50 years.
Gas
If we increase gas production to fill the energy gap left by oil, our known gas reserves only give us just 52 years left.
Coal
Although it’s often claimed that we have enough coal to last hundreds of years, this doesn’t take into account the need for increased production if we run out of oil and gas.
If we step up production to make up for depleted oil and gas reserves, our known coal deposits could be gone in 114 years.
