Investigating Forces and Motion

A car is moving along a straight road. The engine provides a thrust force to speed it up, while the brakes apply friction to slow it down. If the thrust is greater than the friction, what will happen to the car's speed? Use reasoning to explain your answer.

• The car will maintain a constant speed because the forces are balanced.

• The car will slow down because friction always stops motion.

• The car will speed up because the resultant force is in the direction of the thrust.

• The car will move backwards because friction is present.

A box is being pushed from opposite sides with equal forces of 5 N each. Explain, using reasoning and evidence, what will happen to the box and why.

• The box will move to the right with a force of 10 N.

• The box will move to the left with a force of 5 N.

• The box will not move because the forces are balanced.

• The box will move in circles.

Predict what will happen to a spacecraft's motion if its engines suddenly fire and produce a force in the direction of travel, according to Newton's first law.

• The spacecraft will accelerate in the direction of the force because a resultant force is now acting on it.

• The spacecraft will continue at the same velocity because no force can change its motion in space.

• The spacecraft will stop moving because the force cancels its velocity.

• The spacecraft will move in a circle because of the new force.

Given Newton's first law of motion, evaluate the following scenario: A piece of space debris continues moving in a straight line at a constant speed unless it enters the gravitational field of a planet or collides with an asteroid. Explain why this scenario is an example of Newton's first law.

• The debris will continue in its state of motion unless acted upon by a resultant force, such as gravity or collision.

• The debris will always change its speed regardless of external forces.

• The debris will stop moving if it is not in a gravitational field.

• The debris will accelerate even without any external force.

A baseball player hits a ball, causing it to accelerate quickly towards a home run. Using Newton's second law, explain why the ball accelerates so rapidly and what factors influence this acceleration.

• The ball accelerates rapidly because a large resultant force is applied, and its mass is relatively small.

• The ball accelerates rapidly because it is round and smooth.

• The ball accelerates rapidly because it is hit at a high angle.

• The ball accelerates rapidly because it is made of a special material.

A person pushes a lawn mower over long grass and weeds. According to Newton's second law, what must happen for the lawn mower to accelerate, and how does the force applied relate to the mower's mass?

• The lawn mower will only accelerate if a resultant force is applied, and the acceleration will be smaller if the mower's mass is larger.

• The lawn mower will accelerate on its own, regardless of force.

• The lawn mower will accelerate faster if its mass is increased.

• The lawn mower will not accelerate unless it is pulled instead of pushed.

Given Newton's second law, if two objects experience the same resultant force but have different masses, how will their accelerations compare?

• The object with the smaller mass will have a greater acceleration.

• Both objects will have the same acceleration.

• The object with the larger mass will have a greater acceleration.

• Both objects will not accelerate at all.

To solve for mass using the formula triangle for force, mass, and acceleration, which equation would you use if you know the force and acceleration?

• Mass = Force × Acceleration

• Mass = Force ÷ Acceleration

• Mass = Acceleration ÷ Force

• Mass = Force + Acceleration

Given a car of mass 900 kg accelerates at 9 m/s², use Newton’s second law to determine the force required to produce this acceleration. Explain your reasoning and calculation process.

• 810 N

• 900 N

• 8100 N

• 9000 N

• The acceleration increases as mass increases.

• The acceleration remains the same regardless of mass.

• The acceleration decreases as mass increases.

• The acceleration becomes zero as mass increases.