electric truck motor mass
Let's work out thrust first, then consider torque. Thrust is forward force. We will start by ignoring wind resistance just to make the calculations easier.

100 kph = 27.8 m/s.

27.8 m/s / 20 s = 1.4 m/s/s

So you need to accelerate at 1.4 meters / second /second. Thrust force can be found using F = M * A. You gave the mass as 20 tons, which is 20,000 kg.

F = 20,000 kg * 1.4 m/s/s = 28,000 Newtons.

So that is the forward force or thrust needed. The wheel torque is just thrust multiplied by wheel radius. Let's say the wheel radius is 0.5m.

28,000 Newtons * 0.5m = 14,000 Nm of torque at the drive wheel. If there is a reduction gear, then the motor torque could be smaller. Let's say it is a 10:1 total reduction. Then the motor torque could be 1,400 Newton meters.

160 km/hr = 44 m/s.
circumference of 0.5m radius tire is 3.14m.
44 m/s / 3.14m = 14 Hz. So the 10:1 reduction gives a maximum motor speed of  14 * 10 = 140 Hz, which is 8400 RPM.

So, you would be looking for a motor which can produce more than 1400 Newton meters of torque at moderate speeds, and has a maximum speed of 8400 RPM or more. The motor may not need to produce full torque at 8400 RPM.

My main takeaway from this is that you definitely want to use a multi-speed transmission. Because the motor specification doesn't sound very reasonable. But hopefully you can do some of your own calculations now.

There is one more thing to calculate. Motor power is motor speed * motor torque, except that speed has to be measured in radians per second. The power of a motor will usually be specified at its "rated speed."

Let's say our motor rated speed is 1800 RPM (a ballpark figure) and torque is 1400 Nm.

1800 RPM = 30 Hz.

30 * 2 * pi = 188.5 rad/sec.

So motor power is 188.5 rad/sec * 1400 Nm = 264 kW.
264 kW is around 350 HP.

Note that a typical industrial motor will produce constant torque from very low speed all the way up to rated speed. It can also produce more torque for short periods, but may overheat if it produces extra torque for an extended period.

Hope that helps. It is hard to find all this information in one place.