Mass Weight and Gravity

Mass, Weight, Gravity Review

Open Ended

How are you feeling today?

Open Ended

If the mass of a watermelon is 5 kg on Earth, what would its mass be on the moon (g=1.6m/s²)?

Open Ended

If the mass of a watermelon is 5 kg on Earth, what would its weight be on the moon (g=1.6m/s²)?

Mass always stays the same, but weight can change on other planets where the acceleration due to gravity (g) is different than on Earth.

W = mg

Open Ended

A rock is kicked off of a cliff. What is the speed of that rock after it has been falling for 2 seconds?

3s x 9.8m/s²

= 29.4 m/s

Open Ended

A skydiver jumps out of a plane. How fast would they be going after falling for 10 seconds?

10 s x 9.8m/s²

= 98 m/s

Multiple Choice

What is the standard unit for mass?

• kilograms (kg)

• Newtons (N)

• pounds (lbs)

Multiple Choice

What is the standard unit for weight?

• kilograms (kg)

• Newtons (N)

• pounds (lbs)

Open Ended

Solve for w.

m=15 kg

g=9.8m/s²

w=mg

w = mg

w = (15kg)(9.8m/s²)

w = 147N

Open Ended

Solve for m.

w=550N

g=9.8m/s²

w=mg

w = mg

550N = m(9.8m/s²)

550N/9.9m/s² = m

m = 56.12 kg

Multiple Choice

As the distance between two objects increases, the force of gravity

• also increases

• decreases

Multiple Choice

As the mass of one or both objects increases, the force of gravity

• also increases

• decreases

Universal Law of Gravity

 $F=G\ \frac{m1m2}{d^2}$  

Fancy looking equation that basically tells us that
the force of gravity between two objects is based on their masses and distance between them

more mass = stronger gravity
more distance = weaker gravity

**Think about the way magnets interact with eachother as an analogy

Multiple Choice

As the distance between two objects increases, the force of gravity

• also increases

• decreases