5. Forces (weight, mass and gravity, resultant force and work done)

Question 1

What is gravity?

Answer 1

• All matter has a gravitational field, and attracts all other matter
• the larger the mass, the stronger the field, the greater the attraction

Question 2

When does the force of attraction increase? (gravity)

Answer 2

When objects are larger and closer together

Question 3

What is mass?

Answer 3

How much matter is within an object

Question 4

What is mass measured in?

Answer 4

Kg

Question 5

What is weight?

Answer 5

The force acting on an object due to gravity

Question 6

What is weight measured in?

Answer 6

Newtons

Question 7

What is the equation for weight?

Answer 7

Mass (Kg) x Gravitational field strength (N/kg)

Question 8

What is weight directly proportional to?

Answer 8

Mass

Question 9

What do free body diagrams show?

Answer 9

All the forces which act on an object

Question 10

What do the arrows in a free body diagram show?

Answer 10

the size and direction of the force

Question 11

What is resultant force?

Answer 11

The overall force on a point or object

Question 12

What is the gravitational field strength on earth?

Answer 12

9.8

Question 13

What if the same person is on two different planets?

Answer 13

• The person’s mass is the same
• the gravitational field strength at the two planets will be different
• so their weight will be different on both

Question 14

Where is the weight of an object considered to act at?

Answer 14

The object’s centre of mass

Question 15

What is the equation for work done?

Answer 15

work done (J) = force (N) x Distance (m)

Question 16

What is 1J equal to?

Answer 16

1NM

Question 17

What is Newton’s first law of motion?

Answer 17

If the forces acting on an object is balanced, the resultant force is 0

Question 18

If the resultant force of an object is 0, what can this mean?

Answer 18

• that the object is stationary
• or that the object is travelling at a constant speed in one direction