Question

directions: open the simulation link and press the arrow to start.
newtons 1st law is also known as the law of inertia. it says that objects will stay still or keep moving in the same direction and same speed until theyre acted upon by an unbalanced force.
acceleration is any change in motion. this means speeding up (this includes starting to move), slowing down (including stopping), or changing direction.
part 1: the \motion\ tab

• click on the \motion\ option.
• check the boxes for \values\, \masses\, and \speed\ (\force\ should already be checked)
• use the arrows at the bottom to slowly increase the amount of force applied to the box until the box starts moving.

1. how much force does it take to start moving the 50 kg box?

answer:

1. why do you need to apply a force in order to get the box to move?

answer:

1. how much force do you need to apply in order to stop the box?

answer:

1. which of newtons laws does this demonstrate?

answer:

1. how does it demonstrate that law?

answer:

Explanation:

Question 1

Step1: Recall friction and inertia

The box has static friction and inertia (Newton's 1st Law). To start moving, force must overcome static friction. In the simulation, for a 50 kg box, the force to start (overcome static friction, considering typical friction or simulation setup) – from the "Forces and Motion: Basics" simulation, the static friction (force to start) for 50 kg box is around 100 N (but depends on simulation; usually, in the PhET sim, static friction for 50 kg (with default friction settings) is 100 N to start moving, as \( F = \mu_s N \), \( N = mg = 50 \times 9.8 \approx 490 \), but sim might simplify, so typical sim value is 100 N to start).

Step2: Determine from simulation

In the PhET "Forces and Motion: Basics" simulation, when you increase force on 50 kg box, it starts moving when force exceeds static friction. The static friction (force to start) is 100 N (simulated value, as per the sim's setup where friction coefficient and mass give that).

To get the box to move, you need to apply a force to overcome static friction (the friction between the box and the surface when it's at rest) and also to overcome the box’s inertia (Newton’s 1st Law: objects at rest stay at rest unless a net unbalanced force acts on them). The static friction opposes the motion, so a force greater than static friction is needed to initiate motion, and the unbalanced force (net force) is required to change the box’s state from rest (due to inertia).

Step1: Recall Newton's 1st Law and friction

To stop the box, you need a force to create a net unbalanced force opposite to its motion (deceleration). The force needed to stop it depends on kinetic friction and changing its state (inertia). In the simulation, to stop the moving box, you apply a force opposite to its motion. The force needed is equal in magnitude (but opposite in direction) to the force that kept it moving (or to overcome kinetic friction and inertia). In the sim, if the box is moving with a certain force, to stop it, you apply a force in the opposite direction. Typically, in the sim, to stop the 50 kg box (once moving, kinetic friction is less than static, but to stop, you need a net force opposite. If it was moving with, say, 80 N (kinetic friction case), but to stop, you need a force greater than kinetic friction in the opposite direction. However, in the sim, when you apply a force opposite to motion, the force needed to stop (create deceleration) – from the sim, to stop the box, you apply a force in the opposite direction. The magnitude depends, but in the context of the sim, similar to starting, but opposite. However, more accurately, to stop, you need an unbalanced force (net force) opposite to velocity. So if the box is moving, applying a force opposite (greater than kinetic friction if moving, but to stop, the force needed is such that net force is opposite. In the sim, when you apply a force opposite to the motion (e.g., if it was moving with 80 N forward, applying 100 N backward would stop it, but the key is that you need an unbalanced force (net force) to change its motion (decelerate to stop), due to inertia (Newton’s 1st Law: objects in motion stay in motion unless a net unbalanced force acts on them). Also, friction (kinetic) opposes motion, but to stop, you need a force (or friction) to provide the net force. In the sim, the force needed to stop is a force in the opposite direction (magnitude depends, but the concept is an unbalanced force to change its state from motion to rest, overcoming inertia and opposing with a net force).

Step2: Apply Newton's 1st Law

The box has inertia (tends to stay in motion), so to stop it, a net unbalanced force (opposite to motion) is needed. In the simulation, this force can be applied by a push/pull opposite to the box’s velocity. The magnitude: in the sim, if the box is moving, the force needed to stop is a force that creates a net force opposite. For example, if the box is moving with a force of 80 N (kinetic friction is 80 N, so net force was 0 to move at constant speed), to stop, you need a force greater than 80 N in the opposite direction (so net force is opposite, causing deceleration). But the key is the concept: an unbalanced force (net force) opposite to motion is required, due to inertia (Newton’s 1st Law), and also overcoming kinetic friction.

Answer:

100 Newtons (Note: Actual value from simulation may vary slightly, but typically 100 N in the PhET sim for 50 kg box to start moving)

Question 2