A group of kids come across a covered bridge that is a great spot for jumping off, but they want to make sure they stay safe so they want to check how high the
bridge is before anyone jumps off. They find a 5kg rock and guess that it will
experience a coefficient of friction of 0.21 as it falls. Once the rock is thrown over
the edge of the bridge, it takes 1.6s to reach the water.
How tall is the bridge?

As part of your daily workout, you lie on your back and push with your feet against a platform attached to two stiff springs arranged side by side so that they are parallel to each other. when you push the platform, you compress the springs. you do an amount of work of 79.0 j when you compress the springs a distance of 0.230 m from their uncompressed length. (a) what magnitude of force must you apply to hold the platform in this position? (b)how much additional work must you do to move the platform a distance 0.230 m farther? (c) what maximum force must you apply to move the platform a distance 0.230 m farther?