Facts At Your Fingertips: Energy and forces – Forces and movement
Whenever an object changes speed or direction, this happens because a force is acting on it.
More than 300 years ago, the English scientist Isaac Newton worked out three laws of motion that explain how forces affect movement.
First law of motion
The first law states that an object will continue at the same velocity in a straight line if no force is acting on it.
If the object is not moving, it will remain at rest until a force acts on it.
The space probe Voyager 2 is flying through space with almost no forces acting on it to slow it down, so it will continue moving at the same velocity.
Second law of motion
According to Newton’s second law, the greater the force applied, the greater the acceleration.
Acceleration also depends on the mass of the object— the more mass it has, the more force is needed to accelerate it. Motorcycles have much smaller mass than cars and can accelerate very quickly.
Third law of motion
Newton’s third law of motion states that every action has an equal and opposite reaction.
A jet engine attached to an aircraft burns fuel to send out a powerful stream of hot gases behind it. As this jet of gases shoots backward, it pushes the engine forward, and the aircraft with it.
VELOCITY AND ACCELERATION
An object’s velocity is the speed at which it is traveling in a particular direction. An increase in velocity is called acceleration, while a decrease is called deceleration. Race cars have powerful engines and can accelerate to high speeds incredibly quickly—from 0 to 100 mph (160 kph) in under 5 seconds.
THE FORCES OF WIND
Tornadoes are violently destructive storms that form from rotating blocks of air in thunderclouds.
As the hot air rises and the cold air sinks, the two blocks begin to spin, forming a rotating column of superfast winds.
Wind speeds in a tornado can reach more than (480 kph), strong enough to tear down trees and send cars flying through the air