An object is in motion if its distance relative to another object is changing. To tell if an object is moving, you use a reference point. If an object's distance from another object [reference point] is changing. A place or object used for comparison to determine if something is in motion.
Answer:
8 J and 2 J
Explanation:
Given that,
Mass of the rubber ball, m = 1 kg
Initial speed of the rubber ball, u = 4 m/s (in east)
Final speed of the rubber ball, v = -2 m/s (in west)
We need to find the kinetic energy of the ball before it hits the wall, the kinetic energy of the ball after it bounces off the wall.
Initial kinetic energy,
Final kinetic energy,
So, the initial kinetic energy is 8 J and the final kinetic energy is 2 J.
Answer:
Vy = 26 m/s sin 30 = 13 m/s vertical speed
t = Vy / a = 13 m/s / 9.80 m/s^2 = 1.33 sec time to reach Vy = 0
H = Vy t + 1/2 g t^2
H = 13 m/s * 1.33 sec - 1.33^2 * 9.8 / 2 m = 8.62 m
<h2>
Answer: B) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature. </h2>
Explanation:
To start a fire it is more optimal to use a concave mirror than a plane mirror. This is because the concave mirror allows concentrating sunlight at a point (the focal point) on an object that acts as fuel and ignite the fire there.
For this it is necessary the object to be positioned between the center of curvature of the mirror and the mirror (its focus). Thus the rays of the Sun, when converging on the focus, will heat the object and make it burn.
Hence, the correct option is B.
Answer:The higher up an object is the greater its gravitational potential energy. The larger the distance something falls through the greater the amount of GPE the object loses as it falls. As most of this GPE gets changed into kinetic energy, the higher up the object starts from the faster it will be falling when it hits the ground. So a change in gravitational potential energy depends on the height an object moves through.
Explanation: Lifting an apple up 1 metre is easier work than lifting an apple tree the same height. This is because a tree has more mass, so it needs to be given more gravitational potential energy to reach the same height.
