natural 1 Forces We cant see forces but we can feel their effect . - PDF document

12/03/2020 natural 1 Forces We can’t see forces but we can feel their effect . Forces make things: • move or stop • change shape • break • fall to the ground • stay still • float or sink 2 1

12/03/2020 Forces can be… PUSH OR PULL CONTACT AND NON-CONTACT BALANCED OR UNBALANCED 3 Do you know how magnets work? Magnets create a magnetic field around them. This force attracts objects made of iron and steel . This is a photo of a magnet and iron filings . The iron filings show us where the magnetic field is. 4 2

12/03/2020 Magnets attract and repel! Opposite poles attract . Same poles repel . 5 Gravity Gravity is a non-contact, pull force . All masses have gravity. It is a force that pulls towards their centre. This force is only noticeable with very large masses , for example, planets. The Earth ’s gravity pulls everything on or near the Earth Newton discovered gravity. towards its centre. This stops us and our belongings floating away! 6 3

12/03/2020 What’s weight ? Weight is the force with which we are attracted to the ground . It depends on: GRAVITY (N) and our MASS (kg, amount of matter). [weight = mass x gravity] 7 What’s upthrust? Upthrust is a contact, push force applied by water and air . It pushes objects in air and water up . The bigger the VOLUME , the bigger the upthrust. 8 4

12/03/2020 Why do we float? HOW do you think GRAVITY and UPTHRUST need to be? Upthrust needs to be as strong as gravity! GRAVITY UPTHRUST 9 10 5