Physics Forces Quiz 02

If the forces on a block are balanced, then it is safe to say that the block is:

• speeding up only.

• slowing down only.

• constant speed only.

• at rest only.

• constant speed or at rest.

Answer explanation

When forces on a block are balanced, it means there is no net force acting on it. Therefore, the block can either be at rest or moving at a constant speed, making 'constant speed or at rest' the correct choice.

Michelle ran out of gas and tried to push the car to the side of the road. She could not get it to move even though she was on a level surface, the brake was off, and the car was in neutral. Why wouldn't the car move?

• Michelle's forward push was smaller than the backward resistance of friction.

• Michelle's forward push was equal to the backward resistance of friction.

• If the car is not moving, then the force by Michelle must be zero.

• The force of inertia was simply too great for Michelle to overcome.

• Michelle's push could not overcome the force of gravity on the car.

Answer explanation

Michelle's push was equal to the backward resistance of friction, preventing the car from moving. This means that while she applied force, it was countered by friction, resulting in no movement.

Tags

NGSS.MS-PS2-2

At hockey practice, Janine hit a puck across the ice. After it is no longer touching the stick, the puck continues to move because...

• there is a force of motion that keeps the puck going.

• the force from the stick continues to push the puck forward, but it eventually runs out.

• no force is needed for the puck to keep moving at a constant speed.

• ice is cold and slippery.

Answer explanation

The correct choice is that no force is needed for the puck to keep moving at a constant speed. This is due to Newton's first law of motion, which states that an object in motion stays in motion unless acted upon by an external force.

Tags

NGSS.MS-PS2-2

After a lecture on forces in science class, Frank was thinking about the forces acting on a box at rest on his desk. Which statement do you think best represents the forces acting on the box?

• The force of gravity is the only force acting on the box.

• The downward pull of gravity is larger than the upward push of the desk.

• No forces act on the box at rest.

• Earth pulls down and the table pushes up equally on the box.

Answer explanation

The correct choice states that Earth pulls down and the table pushes up equally on the box. This represents the balanced forces acting on the box at rest, where gravity and the normal force from the desk are equal.

Frank is experimenting with a metal ball that he is holding up at the end of a string as shown. Which of the following is the best statement about the forces acting on the ball?

• Frank is pulling up on the ball.

• The ball hangs down tight on the string so the weight of the ball is greater than the pull of the string.

• The ball is not moving so there are no forces involved in this situation.

• The up force of the string is equal to the force of gravity on the ball.

Answer explanation

The correct statement is that the up force of the string is equal to the force of gravity on the ball. This indicates that the ball is in equilibrium, with no net force acting on it.

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NGSS.MS-PS2-4

The force required to accelerate a 2-kg mass at 4 m/s/s is:

• 2 N

• 4 N

• 8 N

• 16 N

Answer explanation

To find the force, use Newton's second law: F = m * a. Here, m = 2 kg and a = 4 m/s². Thus, F = 2 kg * 4 m/s² = 8 N. Therefore, the correct answer is 8 N.

Tags

NGSS.MS-PS2-2

A force of F newtons will give an object with a mass of M an acceleration of A. The same force will give a mass of 2 M an acceleration of:

• A/4

• A/2

• A

• 2A

• 4A

Answer explanation

Using F = M*A, for mass 2M, the acceleration A' is A' = F/(2M) = (F/M)/2 = A/2. Thus, the same force gives a mass of 2M an acceleration of A/2.

Tags

NGSS.MS-PS2-2

On the planet Gamma a 4.0-kg mass experiences a gravitational force of 24 N. What is the acceleration due to gravity on Gamma?

• 0.17 m/s/s

• 6 m/s/s

• 9.8 m/s/s

• 96 m/s/s

Answer explanation

To find the acceleration due to gravity, use the formula F = m * g. Rearranging gives g = F/m. Here, g = 24 N / 4.0 kg = 6 m/s². Thus, the acceleration due to gravity on Gamma is 6 m/s/s.

Tags

NGSS.MS-PS2-2

NGSS.MS-PS2-4

A cart is uniformly accelerating from rest. The net force on the cart must be:

• zero.

• constant.

• decreasing.

• increasing.

Answer explanation

The cart is accelerating uniformly, meaning the net force acting on it is constant according to Newton's second law (F=ma). Thus, the correct answer is that the net force must be constant.

Tags

NGSS.MS-PS2-2

In the graph, the acceleration of an object is plotted against the unbalanced force applied. What is the mass of the object?

• 0.2 kg

• 0.5 kg

• 2.0 kg

• 4.0 kg

• 5 kg

Answer explanation

According to Newton's second law, F = ma. If the graph shows a linear relationship between force and acceleration, the slope gives the mass. If the slope is 2 N/m, then mass = 2 N / 4 m/s² = 0.5 kg.

Tags

NGSS.MS-PS2-2