6. Intro to Forces (Dynamics)

A positive charge $b$ is placed between two other positive charges of equal magnitude, one to its left and one to its right. Four arrows (A, B, C, D) point: A to the right, B to the left, C upward, and D downward. Which of the arrows is in the direction of the net force on charge $b$?

A force $F=10$ N acts along the positive x-axis, and another force $F=10$ N acts along the positive y-axis. What is the magnitude and the coordinate direction angles (with respect to the $x$, $y$, and $z$ axes) of the resultant force?

In the context of vehicle motion, the point at which the brakes are first applied and begin to slow down the vehicle is called the

Which two fundamental forces are essential for the operation of generators and electric motors?

A horizontal beam is supported at points B and D. If the distance between supports is $b$ and $b=60\mathrm{mm}$, and a downward force of $100N$ is applied at the midpoint between B and D, what are the reaction forces at B and D?

A 25-g projectile is fired into a cube of ballistic gel at a velocity of 360 m/s. If the projectile penetrates 15 cm into the gel before stopping, find the average force exerted by the gel onto the projectile. Use kinematics and dynamics (Newton's laws).

As a science fair project, you want to launch an 800 g model rocket straight up and hit a horizontally moving target as it passes 30 m above the launch point. The rocket engine provides a constant thrust of 15.0 N. The target is approaching at a speed of 15 m/s. At what horizontal distance between the target and the rocket should you launch?

Which of the following interactions does not occur due to field forces?

A simply supported beam of length $L$ carries a uniformly distributed load of intensity $w$ (force per unit length) across its entire span. What is the magnitude of the reaction force at each support?

Suppose a 65-kg person jumps from a height of 3.0 m down to the ground. Estimate the decelerating force if the person lands stiff-legged so d ≈ 1.0 cm.

<IMAGE>

Which of the following best describes the components that make up a force vector acting on an object on an inclined plane at angle $\theta$ to the horizontal?

In the context of gravitational forces between two masses, at which point is the force of attraction between them the strongest? (Recall that the gravitational force between two masses $m_1$ and $m_2$ separated by a distance $r$ is given by $F=\frac{G}{r}$ where $G$ is the gravitational constant.)

A 500 g model rocket is on a cart that is rolling to the right at a speed of. The rocket engine, when it is fired, exerts an 8.0 N vertical thrust on the rocket. Your goal is to have the rocket pass through a small horizontal hoop that is 20 m above the ground. At what horizontal distance left of the hoop should you launch?

A child of mass $m$ slides down a frictionless slide inclined at an angle $\theta$ to the horizontal. How large is the normal force of the slide on the child?