Science And Math Quiz Grade 7

It is the right answer beacuse when one positve no. and a negative no. get added, teh both get subtracted and the sign of + or - will be put of the bigger no.

A body is said to be in motion if its position changes with respect to a fixed point. This means that if the body moves from one location to another, it is considered to be in motion. The other options, such as speed changes and direction, may be characteristics of motion but they do not define motion itself. Therefore, the correct answer is that a body is in motion if its position changes with respect to a fixed point.

The frequency of a wave is the number of complete cycles it completes in one second. To find the frequency, we can use the formula: frequency = 1 / time period. In this case, the time period is given as 0.25 seconds. Plugging this value into the formula, we get: frequency = 1 / 0.25 = 4 Hz. Therefore, the frequency of the wave is 4 Hz.

The correct answer is 206. This is the number of bones in the human body. The skeletal system is made up of 206 bones, which provide support, protection, and movement for the body. These bones vary in size and shape and are connected by joints, allowing for flexibility and mobility.

The speed of sound in air is approximately 336 m/s. This can be determined by dividing the distance traveled by the sound wave (168m) by the time it takes for the echo to reach the boy (1 second).

Sound cannot travel in a vacuum because it requires a medium, such as air, water, or solids, to propagate. In a vacuum, there are no particles to vibrate and transmit sound waves. Therefore, sound waves cannot travel through empty space where there is no medium.

If one or more chromosomes are missing in a child at birth, it can cause psychological problems. This is because chromosomes contain genetic information that plays a crucial role in the development and functioning of the brain and nervous system. The absence of certain chromosomes can disrupt the normal development of the brain, leading to various psychological issues such as cognitive impairments, learning disabilities, behavioral problems, and mental disorders.