Lesson 3 – Acceleration Due to Gravity

Minds-On *this slide is not intended to be shown in class Materials: 2 sheets of paper, 1 rubber ball. Demo: Take 2 identical sheets of paper. Show students they are identical. Crumple one sheet into a ball. Hold out the uncrumpled sheet in one hand and the crumpled one in the other. Ask students which will hit the ground first. Release both. Ask students why the crumpled sheet hit the ground first. Part 2: Take crumpled sheet in one hand and a rubber ball in the other. Show students the mass of the rubber ball is greater than the crumpled sheet. Ask them which will hit the ground first. Proceed to drop both (if sheet is crumpled sufficient, they should hit the ground simultaneously). Ask students why they hit the ground simultaneously even though the mass of the rubber ball is greater. Clickers here

Acceleration Due to Gravity Acceleration due to gravity (g) is the acceleration of an object falling vertically towards the Earth’s surface From observation, it would appear that objects fall to the earth at different rates (e.g. a paper ball and a piece of paper dropped from the same height do not hit the ground at the same time) However, if air resistance is neglected, falling objects would only be affected by the earth’s gravity and they fall at the same rate

Gravity on the earth is affected by the earth’s mass, radius, and oblate shape Thus, gravity varies slightly depending on location. In general, the greater the distance from the Earth’s centre, the lower the acceleration due to gravity

Solving Gravity Problems When calculating questions involving free fall one can simply use the five constant acceleration equations (Big 5) for uniformly accelerated motion that have been previously presented Example 1: A ball is thrown directly up with a velocity of 12.1 m/s. Ignore air resistance a)What is the maximum height the ball will reach? b)How long does it take the ball to return to its maximum height & original position?

Solving Gravity Problems

Which Equation to Use?

Solving the Equation

Exit Ticket 1.What is acceleration due to gravity in m/s 2 on earth? 2.Why is gravity not exactly the same everywhere on earth? 3.Why do more massive objects not fall any faster than less massive objects?

Homework Nelson Physics 12 Textbook (2001): Questions