D. Give reasons for the following statements.
1. In winter we rub our hand (palms) to feel warm.
2. A ball thrown up returns to the ground.
3. Machine parts are replaced periodically.
4. It is difficult to walk on a very smooth surface.
5. Normal reaction is not always directed upward.
Answers
Explanation:
1 .friction
2.gravitation force ok.......
Answer:
1. When we rub our palms, friction is produced and in turn, we feel warmth due to the production of heat. So, to get warmth we rub our palms during winters.
2. Since gravity pulls the object toward the earth with a constant acceleration g, the magnitude of velocity decreases as the ball approaches maximum height. ... Direction of velocity and acceleration for a ball thrown up in the air.
3. People can generally manage without a dishwasher for a few days but laundry is a major problem if the washing machine suffers a catastrophic failure, as many owners report, and this often happens with nearly-new machines so replacement is not usually an option and you have to look under the tray in the cutlery drawer to find the Warranty.
4. it is because there is friction present between your shoes and the ground. ... Smooth surfaces: Smooth surfaces have very little friction, very less interaction, very less ridges, and grooves, so we will not have a grip on the surface and we slide and makes it difficult to walk on smooth surfaces.
5. If two surfaces are not in contact, they can't exert a normal force on each other.