Exam 3: Forces

When a muscle contracts it can pull, and when it stretches it can push.

The origin of contact forces is electromagnetism.

If a 50 kg skier is pulled by a rope up a 15° slope, what is the minimum tension in the rope? The coefficient of friction is 0.2.

Two identical boxes are on an inclined plane. Box 1 slides down, while box 2 remains at rest on the incline. What of these statements can we correctly conclude?

What is the difference between mass and weight?

If you pull a sled up a slope, which one of these statements is correct for the magnitude of a normal force?

For the law of gravity equation, F = Gm₁m₂/r², to be dimensionally consistent, what must be the units of universal gravitational constant?

A bird rests at the centre of a thin rope suspended between two poles 0.5 m apart. The rope sags 2 cm under the bird's weight, and the tension in each side is 5 N. What is the mass of this bird?

Using data from Table 3.3, calculate the ratio between the electrostatic force and the gravitational force between the proton and the electron in a hydrogen atom, if the distance between the electron and the proton is r = 5.3 × 10⁹ m. The universal gravitational constant G = 6.67 × 10^-11 m³ kg^-1 s^-2, and Coulomb's constant k = 9.0 × 10⁹ N m²/C².

Which of the following is NOT a fundamental force?

The coefficient of static friction between a set of tires on a car and a steep road is 0.58. What is the steepest angle of the road on which the car can stay at rest without slipping downhill?

Can gravity act as a restoring force? Give an example.

A ball is thrown up in the air. Halfway to its maximal height, what is the net force acting on the ball? Assume that there is no air resistance.

We are trying to move a crate across a rough surface. We keep increasing the force until the crate starts moving. Since there is a range of magnitudes of force applied before the crate starts moving, does this mean that kinetic friction has a range of values as well?

Although gravity accelerates you when you fall freely, it is possible to achieve a constant velocity after you jump from an airplane.

Some bodies in our solar system are listed in Table 3.1, with masses and radii. -Based on the data in Table 3.1, what is the relationship between the weights of the same object on Earth and the Moon?

Since viscous forces in fluid and air drag are the same in nature, both depend linearly on the object's velocity.

We are trying to move a crate across a rough surface. We keep increasing the force until the crate starts moving. Since there is a range of magnitudes of a force, this means that kinetic friction has a range of values before the crate starts moving.

The SI unit of force is the newton. Express the newton in terms of basic SI dimensions, mass M, length L, and time T.

Normal force is always a response of a surface to the entire weight of the body.