Use the kinematics equation:
d = vt + 1/2at^2.
In this problem,
v = 15 m/s.
a = 3 m/s^2,
t = 10 s,
So:
d = 15(10) + 1/2*(3)*(10^2) = 300 meters
Let's write the equations of motion on both x- (horizontal) and y- (vertical) axis. On the x-axis, it's a uniform motion with constant velocity vx. On the y-axis, it is a uniformly accelerated motion with initial height h=90 m and acceleration of
pointing down (so with a negative sign):
First, let's find the time at which the jumper reaches the ground. This happens when Sy(t)=0:
and so
Then, we can find the horizontal speed. In fact, we know that at the time t=4.28 s, when the jumper reached the ground, he covered exactly 180 m, so Sx=180 m. Using this into the law of motion in x, we find
Answer:
A. he can hear music coming from the radio.
Explanation:
Jeff knows that the radio produces sound energy because he can hear music coming from the radio.
The music from the radio is a form of sound energy.
- Sound energy is a form of energy dissipated from a body and can be discerned by humans.
- Sound is a mechanical wave that requires a material medium for its propagation.
- It travels by series of rarefaction and compression along its path of motion.
- Since sound energy is an energy in motion, it is a kinetic energy.
- It travels parallel to its source and therefore, it is a longitudinal wave.
Friction is the force that acts on the opposite side of direction of force, thus it manages to decelerate an object, so it acts upward along the plane