Unit 1 - Forces, Movement, Shape and Momentum 1

What is the main difference between a vector and a scalar?

• A vector has magnitude and direction

• A scalar has direction

• A vector has only magnitude

• A scalar has both magnitude and direction

Answer explanation

The main difference is that a vector has both magnitude and direction, while a scalar only has magnitude. Therefore, the correct choice is that a vector has magnitude and direction.

Which of the following is a scalar quantity?

• Force

• Distance

• Acceleration

• Velocity

Answer explanation

Distance is a scalar quantity as it only has magnitude and no direction. In contrast, force, acceleration, and velocity are vector quantities, which have both magnitude and direction.

What unit is used to measure force?

• Kilograms (kg)

• Joules (J)

• Newtons (N)

• Meters (m)

Answer explanation

Force is measured in Newtons (N), which is the standard unit in the International System of Units (SI). Kilograms (kg) measure mass, Joules (J) measure energy, and Meters (m) measure distance.

According to Newton's first law, what happens to an object with constant velocity?

• It will change direction

• It will remain at constant velocity unless acted on by a resultant force

• It will slow down

• It will speed up

Answer explanation

According to Newton's first law, an object with constant velocity will not change its state of motion unless a resultant force acts on it. Therefore, it will remain at constant velocity unless acted on by a resultant force.

What does Newton's second law state?

• Weight is mass times gravitational field strength

• Force equals mass times acceleration

• An object at rest stays at rest

• For every action, there is an equal and opposite reaction

Answer explanation

Newton's second law states that force equals mass times acceleration (F=ma). This means the force acting on an object is directly proportional to its mass and the acceleration it experiences, making this the correct choice.

What is the formula for weight?

• W = g/m

• W = a/m

• W = m × g

• W = m/a

Answer explanation

The formula for weight (W) is given by W = m × g, where m is mass and g is the acceleration due to gravity. This shows that weight is directly proportional to mass and gravity, making this the correct choice.

What is the gravitational field strength on Earth?

• 10 N/kg

• 11 N/kg

• 12 N/kg

• 9.8 N/kg

Answer explanation

The gravitational field strength on Earth is approximately 9.8 N/kg. The closest answer choice is 10 N/kg, which is often rounded for simplicity in calculations.

What happens to a body falling in a uniform gravitational field without air resistance?

• It decelerates

• It reaches terminal velocity immediately

• It does not accelerate

• It accelerates at a constant rate

Answer explanation

In a uniform gravitational field without air resistance, a body accelerates at a constant rate due to gravity, typically 9.81 m/s². This means it continues to speed up as it falls, making 'It accelerates at a constant rate' the correct choice.

What is the effect of air resistance on a falling object?

• It increases the object's weight

• It causes the object to accelerate faster

• It balances the weight of the object

• It decreases the object's speed

Answer explanation

Air resistance acts in the opposite direction to the weight of the object. As it increases, it balances the weight, leading to a constant speed (terminal velocity) rather than accelerating faster or increasing weight.

What is the relationship between mass and weight?

• Mass is the force of gravity on an object

• Weight is the amount of matter in an object

• Mass is measured in Newtons

• Weight is mass times gravitational field strength

Answer explanation

Weight is defined as the force exerted by gravity on an object, which can be calculated using the formula: Weight = Mass × Gravitational Field Strength. Thus, the correct relationship is that weight is mass times gravitational field strength.