Newton’s Laws 10min test

• q1Motion direction

pull

Weight (force due to gravity – don’t just say ‘gravity’)

Friction (opposite to the motion)

Contact force

Show forces as pulls, not pushes in these diagrams, and show object as a point or a box

1c

• If the object is accelerating, either getting faster or slower, then one forces must be bigger than the force opposite to it.

q2

• Newton’s first law:

• if there is no resultant force acting on an object then it will not change its velocity

• (that means it will stay at rest or, if already moving, will continue in a straight line at a steady speed)

q3

• Newton’s second law:

• If there is a resultant force acting on an object then it will change its velocity

• That means it will either get faster or slower or it will change its direction of motion. This law gives us an equation:

• F=ma where F is the resultant force and ‘a’ is the acceleration that the mass m has

q4

• Pull = 20N, Friction = 6N

• So resultant force = 20-6 = 14N

• Mass = 7kg

• F=ma gives us 14 = 7a

•

• so acceleration a = 2m/s2

q5• Mass is the amount of substance in a body

• Weight is the force of the earth’s gravity pulling the mass downwards

• b) Using F=ma we have

• Weight = mass x 10 because gravity always accelerates mass at 10m/s2 on the earth (called g). But mass has to be in kg

• So 300g (0.3kg) has a weight of 3N