4.3 net force extra practice

The gray shaded dot represents a bucket you are lifting up. You apply a force of 25 N and the weight of the bucket is -10 N. Which vector is 25 N? Click in the correct dot.

The gray shaded dot represents a bucket you are lifting up. You apply a force of 25 N and the weight of the bucket is -10 N. Which vector is -10 N? Click in the correct dot.

Answer explanation

Gravity always pulls down on masses and that force is their weight. F_g

I label down forces as negative in these problems.

The gray shaded dot represents a bucket you are lifting up. You apply a force of 25 N and the weight of the bucket is -10 N. Which dot is by the correct net force on the bucket? Click in the correct dot.

Answer explanation

To find net force, you add the up and down forces together.

Net force = 25 N + - 10 N = 25 N - 10 N = 15 N

The gray shaded dot represents a bucket you are lifting up. You apply a force of 15 N and the weight of the bucket is -8 N. Which dot is by the correct net force on the bucket? Click in the correct dot.

Answer explanation

To find net force, you add the up and down forces together.

Net force = 15 N + - 8 N = 15 N - 8 N = 7 N

Tags

NGSS.MS-PS2-2

The gray shaded dot represents a bucket you are lifting up. You apply a force of 20 N and the weight of the bucket is -5 N. Which dot is by the correct net force on the bucket? Click in the correct dot.

Answer explanation

To find net force, you add the up and down forces together.

Net force = 20 N + - 5 N = 20 N - 5 N = 15 N

You lift a 2-kg bucket with a force of 40.4 N. The weight of the bucket is -19.6 N.

m (bucket) = ​ (a)   F_g (bucket) = ​ (b)   Force applied on bucket = ​ (c)  

• 2 kg
• -19.6 N
• 40.4 N
• 60 N
• 0.8 N
• 14.4 N
• none of these
• 20.8 N

Answer explanation

The force up is 40.4 and the force down is
-19.6 N.

Add these to get the net force.

40.4 + - 19.6 N = 40.4 - 19.6 = 20.8 N

To get net force, always add up to down and left to right.

You lift a 3-kg bucket with a force of 50 N. The weight of the bucket is -29.4 N.

m (bucket) = ​ (a)   F_g (bucket) = ​ (b)   Force applied on bucket = ​ (c)  

• 3 kg
• -29.4 N
• 50 N
• 60 N
• 0.8 N
• 14.4 N
• none of these
• -30.4 N
• 20.6 N

Answer explanation

The force up is 40.4 and the force down is
-19.6 N.

Add these to get the net force.

40.4 + - 19.6 N = 40.4 - 19.6 = 20.8 N

To get net force, always add up to down and left to right.

You lift a 2-kg bucket with a force of 40.4 N. The weight of the bucket is -19.6 N.

m (bucket) = ​ (a)   F_g (bucket) = ​ (b)   Force applied on bucket = ​ (c)   Net force on bucket = ​ (d)  

• 2 kg
• -19.6 N
• 40.4 N
• 20.8 N
• 60 N
• 0.8 N
• 14.4 N
• none of these

Answer explanation

The force up is 40.4 and the force down is
-19.6 N.

Add these to get the net force.

40.4 + - 19.6 N = 40.4 - 19.6 = 20.8 N

To get net force, always add up to down and left to right.

Tags

NGSS.MS-PS2-2

You lift a 1-kg bucket with a force of 10.2 N.

m (bucket) = ​ (a)   F_g (bucket) = ​ (b)   Force applied on bucket = ​ (c)   Net force on bucket = ​ (d)  

• 1 kg
• -9.8 N
• 10.2 N
• 0.4 N
• 20 N
• 0.8 N
• 1.4 N
• none of these

Answer explanation

Mass is measured in kilograms

m = 1 kg

Weight is a force: F_g = mg

F_g = 1 kg · -9.8 m/s² = -9.8 N

This is the force down on the bucket

The force up is 10.2 N

The net force is the sum of the forces

10.2 N + - 9.8 N or 10.2 N - 9.8 N = 0.4 N

Tags

NGSS.MS-PS2-2

You lift a 4-kg bucket with a force of 50.2 N. What is the net force on the bucket?

m (bucket) = ​ (a)   F_g (bucket) = ​ (b)   Force applied on bucket = ​ (c)   Net force on bucket = ​ ​ (d)  

• 4 kg
• -39.2 N
• 50.2 N
• 20 N
• 0.8 N
• 1.4 N
• 16.6 N
• 11 N
• 89.4 N
• 14 N

Answer explanation

Mass is measured in kilograms

m = 4 kg

Weight is a force: F_g = mg

F_g = 4 kg · -9.8 m/s² = -39.2 N

This is the force down on the bucket

The force up is 50.2 N

The net force is the sum of the forces

50.2 N + - 39.2 N or 50.2 N - 39.2 N = 11 N

Tags

NGSS.MS-PS2-2