MediumPhysicsHigh School (9–10)GeneralMechanics › GravitationConceptual

A student says: 'The Earth pulls a 3 kg stone twice as hard as a 1.5 kg stone, so the heavy stone…

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A student says: 'The Earth pulls a $3\ \text{kg}$ stone twice as hard as a $1.5\ \text{kg}$ stone, so the heavy stone must fall twice as fast.' Find the pull on each stone and the acceleration of each. Is the student right?

Need a reminder? The key ideaShow

Near a planet, $g = \dfrac{GM}{R^2}$ ; at a distance $r$ from its centre, $g$ falls as $\dfrac{1}{r^2}$ . On the Earth's surface $g = 9.8\ \text{m/s}^2$ ; at $n$ Earth radii above the ground it is $\dfrac{9.8}{(1 + n)^2}\ \text{m/s}^2$ .

The worked solution

Have you tried it?

Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.

← All Problems

← Nobody can put the Earth on a scale, but we can find its mass from g.A 5 kg object is on the ground, then at heights of 1R, 2R, 3R and 4R above the ground, where R is… →

More onMechanics › Gravitation

Discussion (0)

Loading…