The force is given by F = -dU/dx (i.e. the negative of the graph’s gradient); dU/dx is sometimes called the potential gradient.

Remember to use SI units (metres for distance) when finding gradient:

When x=5cm, dU/dx = (0-20)/(0.10-0) = -200 J/m

F = -(-200) = 200N

The question asks for 2 significant figures so strictly speaking we should write 2.0×10²N.

When x=15cm, dU/dx = 0 so F = 0 (or maybe you need to write 0.0N).

When x=25cm AND when x=35cm, dU/dx = (20 – 0)/(0.4-0.2) = 100 J/m

F = -100N (negative sign means force acts in the -x direction)

The question asks for 2 significant figures so strictly speaking we should write -1.0×10²N

The force is given by F = -dU/dx (i.e. the negative of the graph’s gradient); dU/dx is sometimes called the potential gradient.

Remember to use SI units (metres for distance) when finding gradient:

When x=5cm, dU/dx = (0-20)/(0.10-0) = -200 J/m

F = -(-200) = 200N

The question asks for 2 significant figures so strictly speaking we should write 2.0×10²N.

When x=15cm, dU/dx = 0 so F = 0 (or maybe you need to write 0.0N).

When x=25cm AND when x=35cm, dU/dx = (20 – 0)/(0.4-0.2) = 100 J/m

F = -100N (negative sign means force acts in the -x direction)

The question asks for 2 significant figures so strictly speaking we should write -1.0×10²N

The force is given by F = -dU/dx (i.e. the negative of the graph’s gradient); dU/dx is sometimes called the potential gradient.

Remember to use SI units (metres for distance) when finding gradient:

When x=5cm, dU/dx = (0-20)/(0.10-0) = -200 J/m

F = -(-200) = 200N

The question asks for 2 significant figures so strictly speaking we should write 2.0×10²N.

When x=15cm, dU/dx = 0 so F = 0 (or maybe you need to write 0.0N).

When x=25cm AND when x=35cm, dU/dx = (20 – 0)/(0.4-0.2) = 100 J/m

F = -100N (negative sign means force acts in the -x direction)

The question asks for 2 significant figures so strictly speaking we should write -1.0×10²N

The force is given by F = -dU/dx (i.e. the negative of the graph’s gradient); dU/dx is sometimes called the potential gradient.

Remember to use SI units (metres for distance) when finding gradient:

When x=5cm, dU/dx = (0-20)/(0.10-0) = -200 J/m

F = -(-200) = 200N

The question asks for 2 significant figures so strictly speaking we should write 2.0×10²N.

When x=15cm, dU/dx = 0 so F = 0 (or maybe you need to write 0.0N).

When x=25cm AND when x=35cm, dU/dx = (20 – 0)/(0.4-0.2) = 100 J/m

F = -100N (negative sign means force acts in the -x direction)

The question asks for 2 significant figures so strictly speaking we should write -1.0×10²N